Which phrase can be represented by an equation? twice as much as a number 12 less than a number half of a number is 15 the difference of 20 and a number

Asales representative from a local radio station is trying to convince the owner of a small fitness club to advertise on her station. the representative says that if the owner begins advertising on the station today, the club's total number of members will grow exponentially each month. she uses the given expression to model the number of club members, in hundreds, after advertising for t months.