a and b can do a piece of work in 10 days , b and c in 15 days , c and a in 12 days . how long will c take to do it ?
"2 c = 1 / 15 + 1 / 12 – 1 / 10 = 1 / 20 c = 1 / 40 = > 40 days answer : d"
divide(multiply(10, const_3), subtract(divide(add(divide(multiply(10, const_3), 12), add(divide(multiply(10, const_3), 10), divide(multiply(10, const_3), 15))), const_2), divide(multiply(10, const_3), 10)))