Answer: a^2
Work Shown:
I'm assuming the "x" means "multiply", and it is not a variable.
a^5 * a^(-3) = a^(5+(-3)) = a^(5-3) = a^2
The rule I'm using is
a^b*a^c = a^(b+c)
The base is always the same. We add the exponents.
The expression a^2 is in the form a^n with n = 2.