A shopper buys cat food in bags of 3 lbs. Her cat eats 3/4 alb each week. How many weeks does one bag last?

Total weight of a bag of cat food = 3 lbs.

Number of lbs the cat eats the food = 3/4 lbs each week.

We need to find the number of weeks does one bag that is 3 lbs last.

In order to find the number of weeks for total 3 lbs of food, we need to to divide 3 lbs by 3/4.

3 : 3/4.

Let us convert division sign into multiplication and flip the second fraction, we get

3 * 4/3.

We can cross out common 3's from top and bottom.

We get 4.

Therefore, in 4 weeks one bag lasts.