Step-by-step explanation:
[tex] \dashrightarrow \quad \rm {a = \dfrac{v -u}{t} } \\ [/tex]
[tex] \dashrightarrow \quad \rm {a = \dfrac{9 -7}{2} \; m \: s^{-2}} \\ [/tex]
[tex] \dashrightarrow \quad \rm {a = \dfrac{2}{2} \; m \: s^{-2}} \\ [/tex]
[tex] \dashrightarrow \quad \underline{\boxed{\bf {a = 1 \; m \: s^{-2}}}} \\ [/tex] (Answer)