The easiest way to explain this would be to use an examplar question. For example:
Ben is given a sequence of numbers and is told to find the median, lower quartile and upper quartile.
A tin contains red, white and blue beads in the ratio red:white:blue = x:2x:x^2
First we should find the total number of beads in the tin:
x + 2x + x^2 = 3x + x^2
In a survey people had to choose either A, B, C or D.
The percentage of people that chose B, C and D are shown here:
B- 25%
C- 35%
D- 30%