Respuesta :
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.