The sale is 33% off notebooks. This can be found by first subtracting .8 from 1.2
1.2-.8=.4 Now divide .4 by 1.2 to get your answer.

=.33
.33=33%
You can also solve this mentally because if you know your basic multiplication tables, 3*4=12 and so

of 12 would equal 8.
Does you understand it now?