System of equations that can be used to find the price of one drink and the price of one bag of popcorn is:
3d + 10p = 41
2d + 2p = 11
Price of a bag of popcorn is $ 3.5
Solution:
Let "d" be the price of one drink
Let "p" be the price of 1 bag of popcorn
Luke spends total of $41 on three drinks and 10 bags of popcorn
3 drinks x price of one drink + 10 bags of popcorn x price of 1 bag of popcorn = 41

3d + 10p = 41 ------ eqn 1
Christopher spend a total of $11 on two drinks and two bags of popcorn
2 drinks x price of one drink + 2 bags of popcorn x price of 1 bag of popcorn = 11

2d + 2p = 11 ------- eqn 2
Eqn 1 and eqn 2 represents system of equations that can be used to find the price of one drink and the price of one bag of popcorn
Let us solve eqn 1 and eqn 2 to find values of "d" and "p"
Multiply eqn 2 by 5
10d + 10p = 55 --- eqn 3
Subtract eqn 3 from eqn 1
3d + 10p = 41
10d + 10p = 55
(-) ------------------------
-7d = -14
d = 2
From eqn 2,
2d + 2p = 11
2(2) + 2p = 11
4 + 2p = 11
2p = 7
p = 3.5
Thus price of 1 bag of popcorn is $ 3.5 and price of one drink is $ 2