Collect the like terms, so move all the things with c on one side and all the numbers on the other
Then you can solve for c alone, so see if you can set it up
-3x-12=-5+c so have can we move the +c on the right hand side to the left side?
What is -3c-c?
Good, so -4c=-5+12 now what is -5+12?
Yup, so -4c=7 now we just have to divide both sides by -4 and you'll have c
Yes, or c=-7/4