Solve using the distributed property -4(2x-5)=4

-4(2x-5)=4

-8x+20=4

-8x=4-20

-8x/-8= -16/-8

x=2

First you multiply -4 times 2x=-8x.
Then you multiply -4 and -5=20
so -8x+20=4
You subtract 20 on outside of the equal sign.(Because if you do something on one side of the equal sign you have to do it to the other side.)
-8x=-16
then you divide -8 on both sides of the equal sign 
x=2

The shelves will hold 270 books in total

8-2x+3x2=6 and six is your answer