To find the average of the first five multiples of 9, we can sum up the multiples and then divide by the total number of multiples.

The first five multiples of 9 are 9, 18, 27, 36, and 45.

Now, add them up:

$9+18+27+36+45=135$9+18+27+36+45=135

Now, divide by the total number of multiples (which is 5):

$\text{Average}=\frac{135}{5}=27$

$Average=5135 =27$

So, the average of the first five multiples of 9 is 27.