X-number
8x-20=15+x (subtract x)
7x-20=15 (then add 20)
7x=35 (then divide by 7)
I think you've got it from now, if not, just do 35 divided by 7. But go over the steps, so that you know how to do these types of questions.
6+9=15
y+9=x
x=30
y+9=30
y=21
The newspaper carrier can deliver 147 newspapers in 3 hours
