Solve mathematics question, . photo.

How do you use the elimination method for this question? explain, because i really want to understand!

What is the area of the triangle 10 13 12

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.