Verified Answer :

not sure if -4+a⁵=8 or -4+5a=8

if it is the first then add 4 to both sides and take the 5th root obtaining \(a= \sqrt[5]{12}\)

if it is the 2nd then add 4 to both sides and divide by 5 obtainint \(a= \frac{12}{5}\)

The answer to your question is 
a=1.64375182