A couple of your friends have asked your help figuring out how much they are paying for an annual membership fee at the gym as well as the cost of
one kick boxing class. Marie went to 10 classes and spent $200 total.
Stephen went to 25 classes and spent $275.
1. Find the cost per class.

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.