Let h = number of hamburgers sold.
Let c = number of cheeseburgers sold.
h + c = 692
c = h - 58
Since the second equation is already solved for c, we can use the substitution method.
h + c = 692
h + h - 58 = 692
2h - 58 = 692
2h = 750
h = 375
375 hamburgers were sold.