We have the following equation
[tex]-7x+47=y[/tex]where,
y is temperature in °C, and
x the height in km.
* temperature change for every km we go up.
[tex]\begin{gathered} x=0\Rightarrow y=47 \\ x=1\Rightarrow y=40 \\ 47-40=7 \end{gathered}[/tex]therefore, the temperature change for each km we go up from the surface is -7 °C
* temperature on the surface is when x = 0
Then, the answer is 47 °C