## Thinking Mathematically (6th Edition)

$\dfrac{2}{5}$
We cancel out common terms that are both in the numerator and the denominator after simplifying. $\require{cancel}=\dfrac{6x^6}{15x^6} \\=\dfrac{6\cancel{x^6}}{15\cancel{x^6}} \\=\dfrac{6}{15} \\=\dfrac{2}{5}$