(a)$9=3 peanuts
1 peanut=$9/3
=$3
(B)$9=2 peanuts+2 pretzels
=(2*3)+2pretzels
=$6+2pretzels
2pretzels=$9-$6
=$3
1pretzel=$3/2
=$1.50
(c)$9=1peanut+1pretzel+1milkshake
=$3+$1.50+1milkshake
=$4.50+1milkshake
1milkshake=$9-$4.50
=$4.50
$4.50/$1.50=3
3 pretzels can be bought with the amount of money to buy 1 milkshake
Hope u understand