Let us calculate the total cost first. Since each book costs 8$ and we have 6 books, we need to multiply 6 by 8 to get the total cost, hence 48$. We the need to calculate the reduction; 20% *48=9.6$. This is the reduction. To calculate the net cost, we need to subtract the reduction from the total cost. Hence, net cost= 48-9.6=38.4$