Answer:
9
Explanation:
What does 8⁴ mean?
It just means: 8 x 8 x 8 x 8
Similarly, 8⁵ means "8 times itself 5 times."
So if you were to write them both out it would be:
(8 x 8 x 8 x 8) x (8 x 8 x 8 x 8 x 8)
That's 8 times itself 9 times. So the missing exponent is 9.
Simpler way: see the exponents of 4 and 5? 4 + 5 = 9, and that's all you have to do in these problems, is add the exponents. But that only works if the number (or the expression) is the same.