From any **addition** fact such as

135 + 423 = 558

we can work out two **subtraction** facts.

Here we get

558 - 135 = 423

and

558 - 423 = 135

This is handy because we can use additions to check subtractions.

**Example 1**

Anna says that

433 - 115 = 318

Use addition to check if she is right or wrong.

**Answer**

318 + 115 = **433**

So Anna is **right**.

**Example 2**

Ben says that

514 - 325 = 219

Use addition to check if he is right or wrong.

**Answer**

219 + 325 = **544 ****not 514**

So Ben is **wrong**.