Multiplication and Division with contract value - solidity

Question

I am trying to insert a if-clause in the following contract to check if the withdrawal (it is a sample bank contract) is less than the 10% of the whole contracts value, i.e. of the complete bank.
When I insert the code as below it gives me an error such as
"UnimplementedFeatureError: Not yet implemented - FixedPointType."
What am I doing wrong?
Can you help me?
Many thanks in advance!!
pragma solidity ^0.4.24;
contract bank{
mapping (address => uint) private balance;
address public Owner;
function WithDrawMoreMoney(uint a) public{
require (balance[msg.sender]>=0);
require (address(this).balance>=0);
require ((a) =< (address (this).balance)*(uint(1.1))); // The problematic line
balance[msg.sender]-=a;
(msg.sender).transfer(a);

Answer 1

check if the withdrawal ... is less than [10%] of the whole [contract's] value
I think you just want this:
require(a <= address(this).balance / 10);
Your code multiplied by 1.1 when I think you meant 0.1, but either way Solidity only has integers. Dividing by 10 works. You also had a typo: =< instead of <=.
If you want to check some other percentage, like 23%:
require(a <= address(this).balance * 23 / 100);
Make sure to do the multiplication first, and always remember to guard against integer overflows.