You and your friend covered a total distance of 72 kilometers in a bicycle race. the distance was covered into 9 equal parts. you covered 4 parts and your friend covered 5 parts.

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.