a is twice as good a work man as b and together they finish the work in 12 days . in how many days a alone can finish the work ?
"wc = 2 : 1 2 x + x = 1 / 12 = > x = 1 / 36 2 x = 1 / 18 a can do the work in 18 days . answer : d"
inverse(divide(inverse(12), add(const_2, const_1)))