An advertising firm has an old computer that can prepare a whole mailing in six hours. With the help of newer model, the job is complete in 2 hours. How long will it take the newer model to take the job alone?
let x = time the old computer takes to complete a whole mailing y = time the newer model takes to complete a whole mailing since x = 6 hours we solve: (1/6) + (1/y) = (1/2) --> we multiply with 6y: y + 6 = 3y --> 6 = 2y --> 3 hours = y
