In order to determine the division equation of the diagram, you consider that in the diagram you have 8 rectangles. From those 8 rectangles, there are 6 rectangles with a different colors. Then, there are 6 rectangles taken from 8.
The previous situation can be written as follow:
[tex]\frac{6}{8}[/tex]the numerator is the colored rectangles, the denominator the total number of rectangles. The previous fraction can be simpified, just as follow:
[tex]\frac{6}{8}=\frac{3}{4}[/tex]