Given that ${\displaystyle \underset{-1}{\overset{2}{}}}f(x)dx=5$ and ${\displaystyle \underset{0}{\overset{2}{}}}f(x)dx=8,$ evaluate the following.

$($a$){\displaystyle \underset{-1}{\overset{0}{}}}f(x)dx$

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$($b$){\displaystyle \underset{0}{\overset{2}{}}}f(x)dx-{\displaystyle \underset{-1}{\overset{0}{}}}f(x)dx$

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Show My Work $($Optional$)$

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