Answer: 1/243
Step-by-step explanation: To simplify the problem shown, our first step is to convert the decimal in the exponent, -2.5, to a fraction.
-2.5 is the same thing as -2 and 1/2 so we have 9^-2 and 1/2 and -2 and 1/2 is the same thing as -5/2 so we have 9^-5/2.
The rest of my work is attached in the image provided.