on a purchase of $ 118 , a store offered a payment plan consisting of a $ 18 down payment and 12 monthly payments of $ 10 each . what percent of the purchase price , to the nearest tenth of a percent , did the customer pay in interest by using this plan ?
"12 * 10 + 18 = 138 ( 18 / 118 ) * 100 = 15.3 answer : e"
multiply(divide(subtract(add(multiply(10, 12), 18), multiply(10, 12)), 118), const_100)