
\begin{enumerate}
\item $\begin{aligned}[t]
d=v \times t & \iff d = 50 \times 5\\
& \iff \underline{d = 250\text{ m}.}
\end{aligned}$

\item $\begin{aligned}[t]
v = d \times t & \iff t = \dfrac{v}{d}\\
& \iff t = \dfrac{80}{10}\\
& \iff \underline{t=8\text{ h}.}
\end{aligned}$

\item $\begin{aligned}[t]
d = v \times t & \iff v = \dfrac{d}{t}\\
& \iff v = \dfrac{\numprint{10000}\text{ m}}{5\times60\text{ s}}\\
& \iff \underline{v \approx 33,33\rm m\cdot s^{-1}.}
\end{aligned}$
\end{enumerate}
