Please don't run your sentences together. Write just one sentence per line, or separate them from one another with the semicolon (;).
Mrs. Robinson bought a novel at the bookstore on sale for 20% off at regular price of 2909
Mr. Chang what (??? )the same novel
The different books are 40% of its regular price of $25
Which person receive the better discount?
First you say "the same novel" and then you say "the different books."
Kindly rework this problem and post it again with additions and corrections.