# Video: Identifying Addition Facts from Related Subtraction Facts

The picture shows that: 17 − 9 = 8. Use the picture to complete the addition sentence: 9 + 8 = ＿.

01:52

### Video Transcript

The picture shows that 17 subtract nine equals eight. Use the picture to complete the addition sentence nine plus eight equals what?

We’re told that the picture shows a subtraction. 17 take away nine equals eight. How does it show this? Well, firstly, we can see that the total number of squares in the row equals 17. This is our starting number in the subtraction.

We can also see that some of the squares are a lighter color of blue. These are the squares that have been taken away and there are nine of them. So, we’ve started with 17 squares and we’ve taken away nine. And the dark blue squares are those that are left. If we take nine away from 17, we have eight left and there are eight blue squares there.

The question asks us to use the picture to complete an addition sentence, nine plus eight equals what? Where can we see the numbers nine and eight on our picture? Nine is the number of light blue squares, and eight is the number of dark blue squares. And if we add them together, we’d get the total number of squares in the row, which we said was 17.

Nine plus eight equals 17. If we know that 17 take away nine equals eight, then we know that we can work backwards and combine the two parts to make 17. Nine plus eight equals 17. Our missing number is 17.