9514 1404 393
Answer:
14
Step-by-step explanation:
The applicable rules of exponents are ...
(a^b)(a^c) = a^(b+c)
(a^b)^c = a^(bc)
__
(7^?)(7^5)^4 = 7^34
(7^?)(7^20) = 7^34 . . . . simplify power of power
7^(?+20) = 7^34 . . . . . . simplify product
? +20 = 34 . . . . . . . . . . equate exponents of the same base
? = 14
