Problem: if a man lost 7 % by selling oranges at the rate of 21 a rupee at how many a rupee must he sell them to gain 42 % ?
Rationale: "93 % - - - - 21 142 % - - - - ? 93 / 142 * 21 = 13.75 answer : e"
annotated_formula: divide(multiply(subtract(const_100, 7), 21), add(const_100, 42))