To determine the number of bacteria at 8:00 a.m., we need to work backwards from the number of bacteria at 9:00 a.m. Using the information given:
- The bacteria doubles every hour.
- At 9:00 a.m., there were 120 bacteria.
To find the number at 8:00 a.m. (which is one hour earlier), we need to divide by 2:
\[ \frac{n}{2} = 120 \] To isolate \(n\), we multiply both sides by 2:
\[ n = 2 \times 120 = 240 \]
So, at 8:00 a.m., there were 240 bacteria.
Therefore, the correct equation that represents the number of bacteria at 8:00 a.m. is:
\[ \frac{n}{2} = 120 \]
And at 8:00 a.m., there were 240 bacteria.