3 cartons = $4.50
(Multiply both sides by 2)
6 cartons = $9
So it would cost $9.
However, let me just add:
—> if the number of cartons it asked about wasn’t an easy number like 6, and you couldn’t just simply multiply by 2 to get the answer, then what you would do is **find how much 1 carton would cost.**
I’ll use the posted question as an example to show this second method.
3 cartons = $4.50
(Divide both sides by 3)
1 carton = $1.50
**(And then you would multiply **both sides** by however many cartons you need to find out about)**.