drinks, x
popcorn, y
9x + 4y = 40.50
3x + 5y = 38.25
Multiply the 2nd row by 3
9x+4y=40.50
9x+15y=114.75
Subtract the 2nd row from the 1st row
−11y=−74.25
Solve for y
Substitute y
9x+4(6.75)=40.50
9x+27=40.50
Subtract 27 from both sides
9x=40.50−27
9x=13.5
Divide both sides by 9
I'll let you do some of the work ;)
Hope this helps