When you click the flag, you may press any numbers. After you press the first number(s), press an operation (+,-,etc). Then, put in your second number. Lastly, press the equal sign to solve for the input. To clear your answer, press the C button.
I made this project using a lot of if__then__else blocks, and quite a few variables. I used a "when sprite is clicked" to make the buttons functional. *It can only do one calculation at a time, please press C again before inputting more numbers.