H + 121 + 31 = 180
H + 152 = 180
H = 180 - 152
H = 28
The engine would need three gallons of gas.
12/4=3
Are You trying to find out the equivalent expression? or...
Ok so for every 1 centimeter you get 10 millimeters. Meaning that if you multiply 20 * 10 you get 200 millimeters and if you multiply 10 * 10 you get 100. Now you subtract 200-100 and you get 100 millimeters.
