Here your base (1.5) is greater than zero, so you have exponential growth here. That " ^ " is the tip-off to exponentiation.
The area of the circular flower bed
=(13÷2)^(2 × pie
≈132.73 sq.feet
the amount of fertilizer needed
132.73÷10
=13.273
Thus 14 bags of fertilizer will be needed
hope it helps