Question

Please help, having trouble with this

Answer 1

it’s -7

Explanation:

because when you subtract the 6 from both sides you get 12x=9x-21 then subtract the 9x from both sides to get 3x=-21 then divide both sides by 3 to get x=-7.

Answer 2

12x+6=9x-15 (subtract variables, smaller one)
-9x. -9x
3x+6=-15 (subtract 6 to both sides)
-6. -6
3x=-21 (divide 3)
x=-9