How to crate a code for compound interest?

Answer 1

for (int x = 0; x < years; x++)
{
money *= 1.02
// For two percent interest rate
}

Answer 2

Yup, basic maths. To add or subtract a percentage of a number to itself:

Positive percentage,
Money * (1 + (<Percentage> / 100)

Negative percentage,
Money * (1 - (<Percentage> / 100)