Answer: the price of a bag of popcorn is $5.3
Step-by-step explanation:
Let x represent the price of one drink.
Let y represent the price of one bag of popcorn.
Robert spends a total of $65.25 on 4 drinks and 9 bags of popcorn. This is expressed as
4x + 9y = 65.25- - - - - - - - - - - - - - -1
Robert spends a total of $51.75 on 8 drinks and 3 bags of popcorn.
This is expressed as
8x + 3y = 51.75- - - - - - - - - - - - - - -2
Multiplying equation 1 by 8 and equation 2 by 4, it becomes
32x + 72y = 522
32x + 12y = 207
Subtracting, it becomes
60y = 315
y = 315/60
y = 5.25