\((5)(5^4)(x^3)(x^8)\)
5^4 multiplied by 5 is the same as 5^5.
\((5^5)(x^3)(x^8)\)
When two same variables with exponents are multiplied, the exponents add together.
\((5^5)({x}^{11})\)
Expand the 5^5.
\((5*5*5*5*5)({x}^{11})\Rightarrow (3125)(x^{11})\)
So your answer is:
\(3,125x^{11}\)