Suppose that of all used cars of a particular year, 30% have bad brakes. You are considering buying a used car of that year. You take the car to a mechanic to have the brakes checked. The chance that the mechanic will give you wrong report is 20%. Assuming that the car you take to the mechanic is selected " at random" from the population of cars of that year. The odds in favor of chance that the car's brakes are good given that the mechanic says its brakes are good is m : n then (m – 7n) equals. (Where m & n are co-prime natural numbers)