Notes

Difference set is…

Difference set is the difference of sets A and B is the set consisting of all elements of A that are not included in the elements of B.
For example;
$A=\left\{\mathrm{2,\; 4,\; 6,\; 8}\right\},$
$B=\left\{\mathrm{2,\; 3,\; 4,\; 5,\; 6,\; 7,\; 8}\right\}$
$\mathrm{then\; difference\; set}=\left\{\mathrm{3,\; 5,\; 7}\right\}.$