Answer:
[tex]\frac{7}{x^3}[/tex]
Step-by-step explanation:
To divide an algebraic expression, divide the common parts of the term: constants with constants and variables with variables.
[tex]\frac{21x^2}{3x^5} = \frac{21}{3} *\frac{x^2}{x^5}= 7 * \frac{1}{x^3} = \frac{7}{x^3}[/tex]