7k + 16 + 4k = 6k + 31
applying the conmutative property:
7k + 4k + 16 = 6k + 31
combining similar terms:
(7k + 4k) + 16 = 6k + 31
11k + 16 = 6k + 31
subtracting 6k at both sides
11k + 16 - 6k = 6k + 31 - 6k
5k + 16 = 31
subtracting 16 at both sides
5k + 16 - 16 = 31 - 16
5k = 15
dividing by 5 at both sides:
5k/5 = 15/5
k = 3