15.
It is: 21
9
3 - (-12) = 3 + 12 = 15.
15
-12
11
- 15 = 3X - 12add 12 to each side12 + - 15 = 3X - 12 + 12- 3 = 3Xdivide both sides integers by 3- 3/3 = (3/3)X- 1 = X======check in original equation- 15 = 3(- 1) - 12- 15 = - 3 - 12- 15 = - 15=========checks
It is 15 followed by 6 then 18
15
(plus) + 4 (minus) - 3
9