i sold a book at a profit of 10 % . had i sold it for $ 150 more , 15 % would have been gained . find the cost price ?
"115 % of cost - 110 % of cost = $ 150 5 % of cost = $ 150 cost = 150 * 100 / 5 = $ 3000 answer is c"
divide(multiply(divide(multiply(150, 10), subtract(15, 10)), const_100), 10)