Cedric and Zelda went shopping at Price buster buster Cedric Bought to jumbo rolls of aluminum foil and three packages of AA batteries for a total cost of $21 Zelda Bought 5 identical jumbo rolls of aluminum foil and two identical packages of AA batteries for a total cost of $25 find the cost of one roll of aluminum foil and find the cost of one package of AA batteries

Let f and b be the cost of foil and batteries respectively. We are first given that:

2f+3b=21 subtract 3b from both sides

2f=21-3b divide both sides by 2

f = (21-3b) / 2

Then we are given:

5f+2b=25, using f found above in this equation gives you:

5 (21-3b) / 2+2b=25

(5 (21-3b) + 4b) / 2=25 multiply both sides by 2

5 (21-3b) + 4b=50 carry out indicated operations on left side

105-15b+4b=50 combine like terms on left side

105-11b=50 subtract 105 from both sides

-11b=-55 divide both sides by - 11

b=5, since f = (21-3b) / 2

f = (21-3*5) / 2

f=3

So batteries cost $5 and foil cost $3.