$(1$ point$)$ Let ${\displaystyle \underset{6}{\overset{10\mathrm{.}5}{}}}f(x)dx=5,{\displaystyle \underset{6}{\overset{7\mathrm{.}5}{}}}f(x)dx=9,{\displaystyle \underset{9}{\overset{10\mathrm{.}5}{}}}f(x)dx=4$

Find ${\displaystyle \underset{7\mathrm{.}5}{\overset{9}{}}}f(x)dx=$ and ${\displaystyle \underset{9}{\overset{7\mathrm{.}5}{}}}5f(x)-9dx=$