(3 b ^ ? ) ^ 2 means this:
( 3 b ^ ? ) times (3 b ^ ? )
Read the entire problem as 3 times b to the mystery power times 3 times b to the same power equals 9 b ^ 10 .
3 times 3 = 9.
b raised to what power times b raised to that same power = b^10.
That is b^5 because b^5 times b^5 = b^10.
Answer: 5 is the missing power of b
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4 is the missing power for the second question
(m^2 n)^4 = m^(2*4) * n^4 = m^8 n^4