Question

At an airport restaurant, 2 sodas and 4 hamburgers cost $12.00. An order of 4 sodas and 2 hamburgers costs $9.00. How much does one hamburger cost?

Answer 1

Let the cost of soda be s.
Let the cost of hamburgers = h

$\begin{cases} &2s + 4h = 12 ----- (1) \\&4s + 2h = 9 ----- (2)\end{cases}$

Multiply Equation (1) by 2 :
$\begin{cases} &4s + 8h = 24 ----- (1)\\&4s + 2h = 9 ----- (2)\end{cases}$

Equation (1) - (2):
$\begin{aligned} &6h = 15 \\&h = 2.5 \end{aligned}$

Answer: 1 hamburger costs $2.50

Answer 2

Let's say the sodas are each $1. If you have purchased 4 sodas it will cost $4. You still have $5 left on your bill. If you have 2 hamburgers left on your bill the amount of each hamburger is $2.50.