Answer:
$6
Explanation:
let x and y be the number of chip and pretzel bags respectively : 4x%2B2y%3 C=20 : if x=1 then 4%281%29%2B2y%3C=20--->{{2y<=16}}}--->y%3C=8 : if x=3 then 4%283%29%2B2y%3C=20--->{{2y<=8}}}--->y%3C=4 : so chips 1 and pretzels 8 : chips 3 and pretzels 4.