Acertain bacteria doubles the number of its cells every 20min. a scientists puts 50 cells in a culture desk. how many cells will be in the culture dish after 2h.

Every 20 min, the bacteria doubles. So there should be 6 doubling periods in 2 hrs. (2hrs / 20 min = 6) So now you just have to double 50, 6 times. This is essentially 50*  which is equal to 50*64=3200. 3200 is the number of bacteria after you doubled 50, 6 times.

The method to find the female dormitory is 2-d=800