how is the answer 4??

Answer:
see below
Step-by-step explanation:
log sqrt5 (25) = y
we know that loga (b) = c can be rewritten as a^c = b
sqrt(5) ^ y = 25
Rewriting sqrt(5) as 5^1/2 and 25 as 5^2
5^1/2 ^ y = 5^2
we know a^b^c = a^ (b*c)
5 ^ 1/2y = 5^2
1/2y = 2
y = 4