How can limit how many times an operator shows up in my maths quiz in vb? - vb.net

Question

My task was to create a 10 question maths quiz with 2 random numbers and a random operator (only +, - or *) for each question. Also the program must ask for the users name. Which I have done.
But as my quiz has only 10 questions, there is a very small probability that one of the operators will be in the majority or that one may not show up. So basically I need something that can limit how many times each operator shows up, for example each operator can only show up 4 times.
As you can see from my code, I'm coding in form. I would be very grateful if you could help me with this as I couldn't find anything on the internet for it and I'm also not too sure how to go about solving this problem either.
Private Sub StartTheQuiz()
number1 = randomizer.Next(1, 13)
number2 = randomizer.Next(1, number1)
leftpluslbl.Text = number1.ToString
rightpluslbl.Text = number2.ToString
userinput.Value = 0
Correct.Visible = False
Incorrect.Visible = False
End Sub
Public Sub TheOperator()
Randomize()
operation = randomizer.Next(1, 4)
addmintime = operation
If addmintime = 1 Then
answer = number1 + number2
operatorlbl.Text = "+"
Userinput.Value = useranswer
ElseIf addmintime = 2 Then
answer = number1 - number2
operatorlbl.Text = "-"
Userinput.Value = useranswer
ElseIf addmintime = 3 Then
answer = number1 * number2
operatorlbl.Text = "x"
Userinput.Value = useranswer
End If
End Sub
Public Function CheckTheAnswer()
If userinput.Value = answer Then
Return True
Else
Return False
End If
End Function
Private Sub Start_Click(sender As Object, e As EventArgs) Handles Start.Click
If NameBox.Text = "What is your name? Enter your name here" Then
NameBox.BackColor = Color.Red
NextBtn.Visible = False
Check.Visible = False
Else
StartTheQuiz()
NameBox.BackColor = Color.LimeGreen
Start.Enabled = False
Start.Visible = False
TheOperator()
question = 0
score = 0
Check.Visible = True
NameBox.Enabled = False
End If
End Sub
Private Sub Check_Click(sender As Object, e As EventArgs) Handles Check.Click
If CheckTheAnswer() = True Then
Correct.Visible = True
Incorrect.Visible = False
question = question + 1
score = score + 1
ElseIf CheckTheAnswer() = False Then
Correct.Visible = False
Incorrect.Visible = True
question = question + 1
score = score + 0
End If
NextBtn.Visible = True
Check.Visible = False
End Sub
Private Sub NextBtn_Click(sender As Object, e As EventArgs) Handles NextBtn.Click
If question < 10 Then
StartTheQuiz()
TheOperator()
Check.Visible = True
NextBtn.Visible = False
ElseIf question >= 10 Then
MessageBox.Show("You have scored " & score & "/10")
MessageBox.Show("Goodbye")
Me.Close()
End If
End Sub
End Class

Answer 1

Here's an example of what I mentioned in the comments. It builds a list of the desired number of operations in equal quantities, then shows how to pull a random one from that list:
Public Class Form1
Private Operations As New List(Of String)
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Operations = CreateOperations(10)
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
If Operations.Count > 0 Then
Dim operation As String = NextRandomOperation()
Debug.Print(operation)
Else
Debug.Print("No more operations in list!")
End If
End Sub
Private Function CreateOperations(ByVal NumberOperations As Integer) As List(Of String)
Dim operators() As String = {"+", "-", "X"}
Dim operations As New List(Of String)
While Operations.Count < NumberOperations
Operations.AddRange(operators)
End While
While Operations.Count > NumberOperations
Operations.RemoveAt(Operations.Count - 1)
End While
Return operations
End Function
Private Function NextRandomOperation() As String
Static R As New Random
If Operations.Count > 0 Then
Dim index As Integer = R.Next(Operations.Count)
Dim operation As String = Operations(index)
Operations.RemoveAt(index)
Return operation
End If
Return ""
End Function
End Class

Answer 2

The proposed solution above will always produce four +, three - and three X. If you want a more random distribution you need to randomize the operators() array.
Dim rnd As New System.Random
Dim operators() As String = New String() {"+", "-", "X"}.OrderBy(Function() rnd.Next).ToArray