At a certain diner, a hamburger and coleslaw cost $3.95, and a hamburger and french fries cost $4.40. If french fries cost twice as much as coleslaw, how much do french fries cost?

Question

Arjun Sharma · Accepted Answer

Define the variables:   Let H be the cost of a hamburger.   Let C be the cost of coleslaw.   Let F be the cost of french fries.
 Write down the given equations:   H + C = 3.95  (Equation 1)   H + F = 4.40  (Equation 2)   F = 2C       (Equation 3)
Substitute the value of F from Equation 3 into Equation 2:   H + 2C = 4.40
Now we have two equations:   H + C = 3.95  (Equation 1)   H + 2C = 4.40
Subtract Equation 1 from the modified Equation 2:   (H + 2C) - (H + C) = 4.40 - 3.95   H + 2C - H - C = 4.40 - 3.95   C = 0.45
Substitute the value of C back into Equation 3 to find F:   F = 2C   F = 2 * 0.45   F = 0.90
Therefore, the cost of french fries is $0.90.