Problem: a and b together can do a work in 4 days . if a alone can do it in 20 days . in how many days can b alone do it ?
Rationale: "b 5 1 / 4 â € “ 1 / 20 = 1 / 5 = > 5"
annotated_formula: add(inverse(subtract(divide(const_1, 4), divide(const_1, 20))), divide(const_2, add(const_2, const_3)))