a can do a piece of work in 30 days ; b can do the same in 30 days . a started alone but left the work after 10 days , then b worked at it for 10 days . c finished the remaining work in 10 days . c alone can do the whole work in ?
10 / 30 + 10 / 30 + 10 / x = 1 x = 30 days answer : a
divide(10, subtract(const_1, divide(add(10, 10), 30)))