working alone , printers x , y , and z can do a certain printing job , consisting of a large number of pages , in 12 , 25 , and 30 hours , respectively . what is the ratio of the time it takes printer x to do the job , working alone at its rate , to the time it takes printers y and z to do the job , working together at their individual rates ?
"p 1 takes 12 hrs rate for p 2 p 3 together = 1 / 25 + 1 / 30 = 11 / 150 therefore they take 150 / 11 ratio = 150 / 11 = d"
divide(12, divide(const_1, add(divide(const_1, 25), divide(const_1, 30))))