Question

What is the value of the x variable in the solution to the following system of equations?
7x - 2y = 21
4x + y = 57

21

-21

9

-9

Answer 1

If you double the second equation, you obtain:
8x + 2y = 114.

Note the first equation, too:
7x - 2y = 21
8x + 2y = 114.

If this is not suggestive of anything, look at the y values. What I'm trying to say is to add the two equations:
15 x = 135.
x = 9