Since base is common, apply the product of powers property: a^m · aⁿ = a^{m + n}.

5³ · 5⁸ = 5^{3 + 8}

= 5¹¹                            (Add  exponents: 3 + 8 = 11)

Product of  5³ · 5⁸ is 5¹¹.