Each day Yohanna will complete four more walking planks than the day before if he starts with five walking planks on the first day how many walking planks will he

do on the 12th day

We need an equation for this.

He starts with 5 and will complete four more than the previous.

5+4 (x-1) = y

The reason we have x-1 is because on the first day, he started with a certain number. If you just did 5+4x, he would have done 9 planks.

Let's solve.

5+4 (12-1)

5+4 (11)

5+44

49

He did 49 planks.