If this was intended to be 25^(3/2), then you can either apply the 3rd power or the second root first:
25^(3/2) = sqrt( 25^3 ) OR 25^(3/2) = ( sqrt(25) )^3
Personally, I’d go with the second approach, because I know sqrt(25) = 5 and I know 5^3 = 125
You could do sqrt( 25^3 ) = sqrt( 15625 ), but I don’t know that value without a calculator.
(A calculator will confirm sqrt ( 15625 ) = 125