Distribute the exponent in the numerator:
[tex]\dfrac{(10w^3)^2}{5w}=\dfrac{10^2w^6}{5w}[/tex]
Then if [tex]w\neq0[/tex], we can cancel one of each [tex]w[/tex] in the numerator and denominator:
[tex]\dfrac{10^2w^6}{5w}=\dfrac{10^2w^5}5[/tex]
Finally, the square of 10 is 100, and 100 divided by 5 is 20, so we're left with (C),
[tex]20w^5[/tex]
