What are you entering for APR? APR is declared as an int, but the text prompting for a decimal makes it sound like you're expecting something like .25 - in which case APR should probably be a double.
If i make the APR a double, it gives me the error "invalid operands of types 'double' and 'int' to binary 'operator'". Basically I can't make that formula work, even though that's the formula the assignment is making me use.
@wildblue the input for APR the "user" is going to enter is 0.12, which means 1 year. The "user" is also entering L to be 10000 and N is 36
The caret ^ is the bit-wise mutually-exclusive OR operator (called XOR).
It doesn't have anything to do with exponents. Take @wildblue's advice and look up std::pow.