Are there are helpful pages or articles that will give me an example of using a program that reads a string that is an expression with two integers and an operator, and will find the answer. Such that if I had:
Google expression evaluation, but that'll probably be much more powerful and complicated than what you need. What operations do you need to implement other than subtraction?
Okay, so then all you need to do is split the string (std::string::substr()) at every minus sign (std::string::find()) and convert what's in between to integers (std::stringstream).
And you don't need an array. Just get the next term and subtract it from the final result.