Let h be the price of a hamburger, d be the price of a hot dog and c be the price of a cheeseburger
3+d=h —(1)
c-20=h —(2)
3h=2d+2c-75 —(3)
Sub (1), (2) into (3)
3h=2(h-3) + 2(h+20) -75
3h =2h-6+2h+40-75
3h=4h-41
h=41
Therefore, the price of a hamburger is $41
