To “solve for c” means to get c by itself.
Step 1: get anything without a c to other side:
2a - 2a + 3c = 17a -2a - 21
3c = 15a - 21
Step 2: get rid of the 3 on 3c. Since 3c means 3•c, you need to divide 3 away:
3c / 3 = (15a-21) / 3
Make sure you divide EVERYTHING on the right (both 15a and -21) by 3.
Do the division and you’ll have your answer.
