Question

Hannah bought 4 hamburgers and 2 orders of french fries at a local restaurant for $16.50. Philip bought 5 hamburgers and 3 orders of french fries for $21.25 at the same restaurant. What is the price, in dollars, of 1 order of french fries?

Answer 1

1 order of french fries are $1.25

Hope this helps 

Answer 2

Let cost of 1 hamburger = h

Let cost of 1 order of french fries = f

Given that "Hannah bought 4 hamburgers and 2 orders of french fries at a local restaurant for $16.50"

So we get equation

4h+2f=16.50

or 2f=16.50-4h

divide both side by 2

or f=8.25-2h...(i)

Given that "Philip bought 5 hamburgers and 3 orders of french fries for $21.25 at the same restaurant."

So we get equation

5h+3f=21.25...(ii)

plug value of f from (i) into (ii)

5h+3(8.25-2h)=21.25

5h+3*8.25-3*2h=21.25

5h+24.75-6h=21.25

-h=21.25-24.75

-h=-3.5

h=3.5

now plug h=3.5 into (i)

f=8.25-2h=8.25-2*3.5=8.25-7=1.25

Hence price of 1 order of french fries = $1.25.