Answer :
The customer originally bought 12 books. If this customer still purchases this number:
1.15 x 5 = 5.75
0.90 x 7 = 6.30
5.75 + 6.30 = $12.05
$13.85 - $12.05 = Customer would have saved $1.80.
Hope this helps! ~ArchimedesEleven
1.15 x 5 = 5.75
0.90 x 7 = 6.30
5.75 + 6.30 = $12.05
$13.85 - $12.05 = Customer would have saved $1.80.
Hope this helps! ~ArchimedesEleven