If you would like to find the solution to the system of equations, you can do this using the following steps:
4c = 3d + 3
c = d - 1
___________
4 * (d - 1) = 3d + 3
4d - 4 = 3d + 3
4d - 3d = 3 + 4
d = 7
c = d - 1 = 7 - 1 = 6
The correct result would be c = 6, d = 7.