Please answer these three ASAP..

Dear Student,
The solution to your 12th query has/have been provided below:
12.
$$\begin{gathered} \mathrm{m}=-3 \\ \mathrm{v}=80 \mathrm{cm} \\ \mathrm{m}=\frac{\mathrm{v}}{\mathrm{u}} \\ -3=\frac{80}{\mathrm{u}} \\ \mathrm{u}=-\frac{80}{3} \mathrm{cm} \end{gathered}$$
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