You can't tell. The volume doesn't tell you the dimensions. It only tells you
what the product of the three dimensions is, but not what anyone of them is.
There are an infinite number of different possibilities.
Example: Volume = 8 cubic feet
The dimensions of the box could be
Length = 2-ft, Width = 2-ft, Height = 2-ft
or
1 x 1 x 8
or
1 x 2 x 4
or
1 x 3 x 2-2/3
or
1 x 5 x 1.6
or
1 x 6 x 1-1/3
or
1 x 7 x 1-1/7
or
2 x 3 x 1-1/3
or
2 x 5 x 0.8
or
2 x 6 x 2/3
or
2 x 7 x 4/7
or
2 x 8 x 1/2
.
.
etc.
8 blocks because 2/10=1/5 so if they total 4/5 then 2/10+2/10+2/10+2/10=8/10=4/5
Answer: 
======================================================
Explanation:
Method 1
We can use the pythagorean theorem to find x.

-----------------------------------
Method 2
Use the sine ratio to find x. You'll need a reference sheet or the unit circle, or simply memorize that sin(60) = sqrt(3)/2

-----------------------------------
Method 3
Similar to the previous method, but we'll use tangent this time.
Use a reference sheet, unit circle, or memorize that tan(60) = sqrt(3)

-----------------------------------
Method 4
This is a 30-60-90 triangle. In other words, the angles are 30 degrees, 60 degrees, and 90 degrees.
Because of this special type of triangle, we know that the long leg is exactly sqrt(3) times that of the short leg.

The short leg is always opposite the smallest angle (30 degrees).
Answer:
-1.75
Step-by-step explanation:
The z-score = (n - m) / d where n is the value (13) m = mean and d = standard deviation.
= (13 - 20) / 4
= -1.75 (answer)