First you have all ten books, but then every time after, you loose one because you can't put the same book in the group twice.
10 * 9 * 8 * 7 = 5040 groups
172,000 is the answer I think
They are based on SSS. They have the middle side which they share and is equal. And those other two lines also make those sides equal, so all sides are equal and they’re congruent
I got 6x+3
The three equations are:
(2x-6) + (3x+1) + (x+8) =perimeter
2x+3x+x/1x=6x
-6+1+8= 3
