18 people in 6 cars
Unit rate

This is a fraction equal to

18 people÷ 6 cars

We want a unit rate where

1 is in the denominator,

so we divide top and bottom by 6

18 people ÷ 6

6  cars ÷ 6

= 3people/1

3 people per car

the entire expression should be subtracted from 30. to subtract the quantity, distribute the negative sign, which changes the signs on the terms. so, the –2 changes to positive and gets added to 30 instead of subtracted from it.

hope this ! ^w^