SAT Mathematics Practice Test 3

A system of equations can be used where h represents the number of calories in a hamburger and f represents the number of calories in an order of fries.
The equation 2h+3f=1700 represents the fact that 2 hamburgers and 3 orders of fries contain a total of 1700 calories, and the equation h=f+50 represents the fact that one hamburger contains 50 more calories than an order of fries.
Substituting f+50 for h in 2h+3f=1700 gives 2(f+50)+3f=1700.
This equation can be solved as follows
2f+100+3f=1700
5f+100=1700
5f=1600
f=320
The number of calories in an order of fries is 320, so the number of calories in a hamburger is 50 more than 320, or 370.