Question 1008107
Call the number of hardcover and paperback books, h and p.
Thus 
h + p = 8  and the value equation is
4h + 2p = 26
Now multiply the top one by four and subtract from the second one...we get
4h + 2p = 26
-(4h + 4p = 32)
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-2p = -6
p = 3  so that
h = 5