Hello, Mukilab!
I'm not sure if I understand the problem,
. . but I'll take a guess . . .
I understand how histograms work and such but I just don't understand this one.
Table:
Complete the histogram. I see no way to fill in the blanks, so I must assume that "blank" means zero frequency.
The frequency represents an area above the interval.
The first interval is [0,10], ten units wide.
The area is 20.
Hence, the height is 2.
The third interval is [15, 17.5], 2½ units wide.
The area is 30.
Hence, the height is: .
The fourth interval is [17.5, 20], 2½ units wide.
The area is 40.
Hence, the height is: .
The histogram looks something like this: Code:

 16
 **
 12::
 **::
 ::::
 ::::
 2 ::::
** ::::
::::::::::: ::::
 +   +   +   + + +   +   +   +   +  
0 5 10 15 20 25 30 35 40