To calculate the total earnings of the surf instructor, we need to consider both Sandra and Bela.
Firstly, we calculate the monthly earnings from Sandra:
[tex]\[
y = 8 \times 32 + 12
\][/tex]
[tex]\[
y = 256 + 12
\][/tex]
[tex]\[
y = 268
\][/tex]
Thus, the instructor receives [tex]$268 a month from Sandra.
Next, we calculate the monthly earnings from Bela:
\[
y = 8 \times 24 + 12
\]
\[
y = 192 + 12
\]
\[
y = 204
\]
Thus, the instructor receives $[/tex]204 a month from Bela.
To find the total amount the instructor makes in a month from both students, we add the amounts from Sandra and Bela:
[tex]\[
268 + 204 = 472
\][/tex]
Therefore, the instructor makes [tex]$\$[/tex] 472$ a month from both Sandra and Bela together.