During the production of biodiesel, glycerin is a waste product and is collected by gravity separation because its sg (1.26) is much higher than that of biodiesel. glycerin is withdrawn from the bottom of the separation tank through a pipe that has p1 = 350 kpa gage, where d = 70 cm and the flowrate is 680 l/s. find the pressure at section 2, which is 0.8 m higher and where the diameter has been reduced to d = 35 cm. assume the flow is inviscid. (gravity acceleration: g = 9.81 m/s2)

Remark
If you know the answer to 

6/6 then you know the answer to 4^6 / 4^6

Both are equal to one. You could expand 4^6 to get a numerical answer.

4^6 = 4096

4096 / 4096 = 1

Edit
See comment  posted by the asker.
Well you could do  it one of 2 ways.

4 * 4 * 4 * 4 * 4 * 4
4 * 4 * 4 * 4 * 4 * 4 * 4 * 4 You can do the cancellation to get

1  
4*4 

1/16 That's one way

or 

you could do this as 

4^6
4^8

1/(4^ (8 - 6) ) = 1/4^2
1 / 4^2 = 1/16  <<<<<< answer

Rule
When the bases are the same and the powers are different and you are dividing you can always subtract the powers.