Fiona is trying to prove that a pair of expressions are equivalent by using substitution. Which pair of expressions have the same value if she substitutes y = 3?

A. 3 (4 minus y) minus 7; 5 + 3 y
B. 9 + y + 4 y - 2 - 3 y; -2 y + 7
C. 5 + y - 2 - 6 y + y; 8 y + 3
D. 2 y + 7 + y - 2 + y; 4 y + 5

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.