Section: Mathematics Usage

31) If 6x - 3y = 30 and 4x = 2 - y then find x + y.

1. -4
2. -2
3. 0
4. 2
5. 4

Multiply the bottom equation by 3 and add the two equations together.

6x - 3y = 30 12x + 3y = 6

18x = 36.

Thus x = 2. Now substitute 2 for x in either equation to determine that y = -6. 2 + (-6) = -4.