Lets say cost of cheeseburgers is x and cost of medium shake is y
so first fast food joint gives 2x+3y=8.98----------1
and nother one gives 7x+2y=15.45-----------------------2
multiply eq1 with 2
and multiply 3 to eq3
4x+6y=17.96
21x+6y=46.35
subtract both eq
-17x= - 28.39
cheese burger cost x=1.67 $ put x in eq1
medium shake cost y=1.88$