I attached the picture of the problem please help I am so confused and would really appreciate it

Answer:
(a^4)^5
Step-by-step explanation:
To express a^20 in the form (a^n)^m
We apply the law of indices :
From the power rule :
(a^n)^m = a^n*m
Hence,
For :
a^20 ; expressing 20 in the form n*m
20 = 4*5
Hence,
a^20 = (a^4)^5