Answer:
6500
Explanation:
In 24 hours, there are 12 times 2 hours, so the bacteria count will increase by 500 twelve times. That is, the increase after 24 hours will be ...
12 × 500 = 6000 . . . bacteria
Since the starting number was 500, the total will be ...
500 + 6000 = 6500 . . . . bacteria after 24 hours
_____
If you like, you can compute the rate of change as 500 bacteria / (2 hours) = 250 bacteria/hour. Then the equation for the number is ...
bacteria = 500 + 250h . . . . . where h is the number of hours.
Filling in h=24, we get
bacteria = 500 + 250(24) = 500 +6000 = 6500 . . . . after 24 hours