A cell divides into two identical copies every 4 minutes. How many cells will exist after 5 hours?

I know the answer is 2^75=3.77789x10^22 but I am unsure how 2^75 turns into 3.77789x10^22. Any help would be greatly appreciated.

First of all, a hand calculator will tell you that. You can also compute it in decimal form using logs

Log10 (2^75) =
75 Log10 (2) = 22.57725

2^75 = 10^22.577 = 10^0.57725 * 10^22
= 3.7789 * 10^22