i sold a book at a profit of 12 % . had i sold it for $ 18 more , 18 % would have been gained . find the cost price ?
"118 % of cost - 112 % of cost = $ 18 6 % of cost = $ 18 cost = 18 * 100 / 6 = $ 300 answer is c"
divide(multiply(divide(multiply(18, 12), subtract(18, 12)), const_100), 12)