Question

If 3x - 9y = 21 and 6x + 3y = 21, which of these could be a value of x or y? Select all that apply.

Answer 1

x = 4

y = -1

Explanation:

3x-9y = 21

6x+3y =21

-2* (3x-9y) = -2*(21)

6x+3y = 21

-6x+18y = -42

6x+ 3y = 21

-6x+6x+18y+3y = -21

21y = -21

y --21/21

y = -1

3x-9y =21

3x - 9*(-1) = 21

3x + 9 =21

3x = 21-9

3x = 12

x = 12/3

x = 4