Either |2 - c| = +(2 - c) = 2 - c or |2 - c| = -(2 - c) = -2 + c
So: |2 - c| + 2c = 13 ---> |2 - c| = 13 - 2c
If |2 - c| = 2 - c ---> 2 - c = 13 - 2c ---> 2 + c = 13 ---> c = 11
If |2 - c| = -2 + c ---> -2 + c = 13 - 2c ---? -2 + 3c = 13 ---> 3c = 15 ---> c = 5