Tracy rakes leaves to her parents .she can rake 4 bags of leaves in 40 minutes .if she continues to rake leaves at this rate, how many bags can she rake in 2 hours

The question can be answered using ratio and proportion.
In 40 minutes, Tracy can rake 4 bags of leaves. In 2 hours (which is equivalent to 120 minutes), how many bag will it be?

Making the equation.
4 : 40 = BAGS : 120
4 x 120 = 40 x BAGS
480 = 40 (BAGS) // Divide both sides by 40
BAGS = 12.

So there will be 12 bags of leaves.