Write the equation
popcorn, x
drinks, y
51.25 = 5x + 5y
122.25 = 15x + 8y
Multiply the 1st row by 3
15x+15y=153.75
15x+8y=122.251
Subtract the 2nd row from the 1st row
7y=31.5
Divide both sides by 7
y=31.5/7
simplify
y = 4.5
Substitute y=4.5 into any of the two equations above
Let's pick the first equation
15x+15y=153.75
15x+15(4.5)=153.75
Simplify
15x+67.5=153.75
Subtract 67.5 from both sides
15x=153.75−67.5
Simplify
15x=86.25
Divide both sides by 15
x=86.25/15
Simplify
x=5.75
Therefore,
x=5.75
y=4.5
Follow along on a piece of paper, it'll help you get it.