Haley's car gets at least 18 miles per gallon. if she plans a trip that is 200 miles, what is the minimum number of gallons she'll need?

Needed gallons for 18 miles = 1
Needed gallons for 200 miles = (1/18)*200
                                                = 11.11 gallons

If you would like to find the minimum number of gallons Haley will need, you can calculate this using the following steps:

18 miles ... 1 gallon
200 miles ... x gallons = ?

18 * x = 1 * 200
18 * x = 200
x = 200 / 18
x = 11.11 gallons

The minimum number of gallons Haley will need is 12 gallons.