a and b can do a piece of work in 8 days . with the help of c they finish the work in 5 days . c alone can do that piece of work in ?
"c = 1 / 5 â € “ 1 / 8 = 3 / 40 = > 40 / 3 = 13 1 / 3 days answer : a"
inverse(subtract(5, divide(5, 8)))