Question

Solve for y in the two equations below using substitution.
3x - 9y = 9
-2x - 2y = 8

Answer 1

C

Explanation:

3x - 9y = 9 → (1)

- 2x +2y = 8 ( subtract 2y from both sides )

- 2x = - 2y + 8 ( divide through by - 2 )

x = y - 4

substitute x = y - 4 into (1)

3(y - 4) - 9y = 9

3y - 12 - 9y = 9

- 6y - 12 = 9 ( add 12 to both sides )

- 6y = 21 ( divide both sides by - 6 )

y =
`(21)/(-6)` = -
`(7)/(2)`