Is this correct? i have tried and want it checking

Question 10jur's car can travel 340 miles on 12 gallons. jack's car can travel 390 miles on16 gallons. which person has the best mileage (miles per gallon) and what istheir mileage?

Kapil needed to buy a long wooden beam. he went to two sawmills that each charge an initial fee plus an additional fee for each meter of wood. the following equation gives the price (in dollars) of a wooden beam from the first sawmill as a function of its length (in meters). p = 5+20xp=5+20x

Joe has a rectangular chicken coop. the length of the coop is 4 feet less than twice the width. the area of the chicken coop is 510 square feet. what is the length of the chicken coup?