For this case we propose a system of equations:
a: Let the variable representing the cost of hardcover books
b: Let the variable representing the cost of paperback books
According to the statement data we have:
[tex]5a + 4b = 100\\b = a-2[/tex]
Substituting the second equation into the first we have:
[tex]5a+4(a-2)=100\\5a+4a-8=100\\9a=100+8\\9a=108\\a=\frac{108}{9}\\a=12[/tex]
Thus, the cost of hardcover books is $12
ANswer:
The cost of hardcover books is $12
