Skill: Choose addition or subtraction

When you read a problem, ask: What is happening to the amounts?

• If amounts are put together or something increases, use addition.
• If something is taken away, or you need to find how many more, how many fewer, an unknown part, or a starting amount, use subtraction.

Example:
Ava has $(246)$ stickers. Ben has $(189)$ stickers. How many more stickers does Ava have than Ben?

Step 1: Understand the situation.
We are comparing two amounts. We are not putting the stickers together. We want the difference between the amounts.

Step 2: Choose the operation.
Comparing to find “how many more” means use subtraction:

$$246-189$$

Step 3: Solve.

$$\begin{array}{r} 246\\ -189\\ \hline 57 \end{array}$$

Step 4: Answer the question.
Ava has $\boxed{57}$ more stickers than Ben.

Always check: Since $(246)$ is greater than $(189)$, the answer $(57)$ tells how much greater it is.