Amusic web site announced that over
4 x 10^9 songs were downloaded by 5 x 10^7
registered users. what is the average number
of downloads per user?

Step-by-step explanation:

Average=total numbers of songs /registered users

Average= 4*10^9/5*10^7

Average=40*10^8/5*10^7

Average=8*10^(8-7)

Average=8*10^(1)

Average=80 songs downloaded per user

To find the surface area of a rectangular prism, you find the area of one side and multiply it by to. Do that for three different sides. For example:
L=2
W=3
H=4
2 x 3=6 x 2=12
3 x 4=12 x 2=24
2 x 4=8 x 2=16
Add them up and you should get the answer. The answer to the example is 52.
You could also use the formula of:
A= 2(wl+hl+hw)