The expression 1.5 x 1.09^t models the housing costs, in thousands of dollars, for summer term t years since Chinedu applied to his college.
Now In general we have the following rule for exponential functions:

Here we have two cases for b:
Case 1: if b<1 , we call it as exponential decay.
Case 2: if b>1 , we call it as exponential growth.
Now let us compare our equation with this general form,
1.5 x 1.09^t
Here b is 1.09, which is greater than 1.
So here we can say that the housing cost is increasing exponentially by a factor or 1.09.