ANSWER
5⁻³
EXPLANATION
Here we can use the quotient property of exponents. If we have a quotient of two exponents with the same base, then:
[tex]\frac{a^b}{a^c}=a^{b-c}[/tex]In this problem the base is 5 and the exponents are 5 and 8:
[tex]\frac{5^5}{5^8}=5^{5-8}=5^{-3}[/tex]