The density of the book is 3cm
Solving for X:
1) y=-8x+6.5 y=-4x+11
2) -8x+6.5=-4x+11
3) -8x=-4x+11-6.5 (Subtract 6.5 from both sides)
4) -8x+4x=11-6.5 (Add 4x to both sides)
5)-4x=4.5
5)x=-1.125
Solving for Y:
y=-8(-1.125)+6.5
y=9+6.5
y=15.5
y=-4(-1.125)+11
y=4.5+11
y=15.5
x=-1.125
y=15.5
or
(-1.125,15.5)
