Answer
$58^{\circ} F$
Work Step by Step
We first notice that for every increase of 0.5 for the $x$-values, we have a decrease of 3 for the $y$-values. This means that the function decreases in a linear manner. Hence, we can extract a linear equation from the table.
Next, we notice that when $x$ is 0, $y$ is 76. Combining the first two observations together, we know that the $y$-intercept is 76. Hence, the equation will be in the form of
$$
\begin{aligned}
y &= mx+76 \\
\end{aligned}
$$
Next, we plug in the ordered pair, (1, 70), into the equation to solve for $m$. Doing so allows us to construct the following equation:
$$
\begin{aligned}
y =70 &=m(1)+76 = m+76\\
\end{aligned}
$$
Solving for $m$, we get that $m=-6$. The equation is, therefore,
$$
\begin{aligned}
y &=-6x+76 \\
\end{aligned}
$$
Since the question asks what the temperature will be 3 hours after the start, we plug in 3 for the $x$-value.
If $x=3$,
$$
\begin{aligned}
y &=-6(3)+76 \\
&=-18 + 76 \\
&=58.
\end{aligned}
$$
Hence, the temperature is $\fbox{$58^{\circ}$ F}$.
