We would add 12 to both sides
-3c - 12 + 12 = -5 + c + 12
Refine it to
-3c = c + 7
Then subtract C from both sides
-3c - c = c + 7 - c
Refine it to
-4c = 7
Divide both sides by -4
-4c/-4 = 7/-4
Then Refine t
c = -7/4
The decimal would then be c = -1.75
