Math in Ruby is mostly what you would expect. + does addition, - does subtraction, * does multiplication, and / does division.
Two other ones you might not know about are 2 asterisks, and %. 2 asterisks are for exponents. 5**2 is 5 to the power of 2, which is 25. % is a little weird. In Ruby, it isn't percent, it is modulo. Modulo is like division, but it gives you the remainder of the division problem.
Use math operations to turn old variables into new ones that the if statement will print true to the console when run.