Find the coefficient of the b7z2\displaystyle {b}^{{7}}{z}^{{2}} term in the expansion of (b+z)9\displaystyle {\left({b}+{z}\right)}^{{9}}.

In the expansion,

(b+z)9=b9++\displaystyle {\left({b}+{z}\right)}^{{9}}={b}^{{9}}+\ldots+ b7z2++z9\displaystyle {b}^{{7}}{z}^{{2}}+\ldots+{z}^{{9}}

(Enter ONLY the coefficient)