What is the degree of the monomial: 5x^15? also show your work!

 The degree of the monomial:  " 5x^(15) "  is:  "15" .  

Explanation:

The degree of a monomial, or the highest degree of a [monomial or polynomial] equation or expression — (for that matter)—is the largest number of the exponent value corresponding to the existing variable raised to the highest exponent value (assuming that there is a variable present).  If there is a variable present—but with "no exponent value"—we assume that the exponent value is: "1" (the implied value of "1").

In this case:  "5x^(15)" ;  there is one (1) variable (which is:  "x" ), and this variable, "x", is raised to the power of "15" (fifteen); 
   so the answer is:  "15" .