A box weighs 7 ounces. When a gift is placed inside the box, the box weighs 21 ounces. Which expression can be used to find the weight of the gift?

Question

A)

21 ÷ 7

B)

21 x 7

C)

21 + 7

D)

21 – 7

Answer 1

Let's take a look at what the question is asking:

A box weighs 7 ounces. When a gift is placed inside the box, the box weighs 21 ounces. Which expression can be used to find the weight of the gift?

We know that the box weighs 7 ounces, and the box plus the gift weighs 21 ounces. From this, we want to find the weight of the gift. If we used algebra to write an equation, we would say that

7 + x = 21 where 7 is the weight of the box, x is the unknown weight of the gift, and 21 is the weight of the box plus the gift.

To solve this, we would subtract 7 from both sides, so x = 21 - 7, or x = 14.

So, based upon our answer choices, D) would be the correct answer.