(A) 2x + 5y = 7
(B) 2x − 5y = 7
(C) 5x + 2y = 7
(D) 5x − 2y =10
(E) 5x − 5y =10
Don't worry about me cheating. I already know the answer is A due to me having the answer sheet. However, I want to know how to work out this problem so that when I am faced with something similar I will know what to do.