Question 643069
log81^(A-4) = -(1/4)
(A-4)log81=-.25
Alog81-4log81=-.25
Alog81=4log81-.25
A=(4log81-.25)/log81
using calculator
A=3.869..

check:
log81^(A-4)
=log[81^(3.869-4)]
=log[81^(-.131)]≈-.2500..