Which is the better 18 cans of cat food for $15 or 12 cans for $9

18 cans = 15 dollars

18/18 cans = 15/18 dollars divide both sides by 18

1 can = 0.83 dollars

1 can = 83 cents <<--- first deal

12 cans = 9 dollars

12/12 cans = 9/12 dollars ... divide both sides by 12

1 can = 0.75 dollars

1 can = 75 cents <<--- second deal

The first deal costs 83 cents per can.

The second deal costs 75 cents per can.

The second deal is the better offer, since it's cheaper per can

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".