Gina and Joey share a 30-ounce box of cereal. By the end of the week, Gina has eaten 1
10
of the box, and Joey has eaten
2
5
of the box of cereal. How many ounces are left in the box?

The amount used= 13.04- 1.9 = 11.14

Iam confused on this my self

Idon't take stuff like this new to me

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.