The equation would be: 253.85 = (15)12.50 + x
The steps for solving the equation are:
253.85 = (15)12.50 + x (Multiply 15 and 12.50.)
15 x 12.50 = 187.50
253.85 = 187.50 + x (Now subtract 187.50 from 253.85)
253.85 - 187.50 = 187.50 - 187.35 + x
66.35 = x
He made $66.35 from commission.