Let, d be the price of drink and
p be the price of a bag of popcorn
the system of equations is:
5d+2p= 38.75
3d+4p= 37.25
-3(5d+2p)= -3·38.75 multiply both sides by -3
5(3d+4p)=5·37.25 multiply both sides by 5
Solve
-15d -6p = -116.25
15d+20p=186.25 +
--------------------------------
0 +14p = 70
14p=70
p=70/14=5
one bag of popcorn is $5