**Answer:**

-20/3

**Step-by-step explanation:**

First simplify the left side of the equation

243^(1/5x)= (243^1/5)^x

=( )^x

= 3^x

Now that the left side is simplified, let's move to the right side

81^(x+5)=( )^(x+5) simplify 81 to base 3^4

= use the product of powers property to multiply the exponents together

=

With both sides simplified, let's rewrite the equation, this time in simplified terms

=

x=4x+20 because both the bases are same, their exponential value must also be equal

-3x=20 solve the algebraic equation for x

x=