12=4+3(1+k)
12=4+3(1+k) Subtract 4 from both sides
8 = 3(1 + k) Divide both sides by 3
8/3 = 1 + k Subtract 1 from both sides
8/3 - 1 = k (1 = 3/3)
8/3 - 3/3 = k
5/3 = k