Solve for unknown variable

The problem is 25^(-4x)=5^(x+8)

I know they need equal bases to solve, but I'm having trouble figuring out how to do that correctly. Help please, and thanks!

Remember basic exponent rules
25=5^2
and
25^y = 5^2y

so
5^2*(-4x) = 5^(x+8)

so, now that we have a common base, the exponents must be equal.

-8x = x + 8
-9x = 8
x=-8/9