Y=mx+b, where m is the slope and b is the y-intercept (the value of y when x=0)
We are told the slope is 4 so
y=4x+b, now using point (-7,-6) we can solve for the y-intercept...
-6=4(-7)+b
-6=-28+b
22=b so our line is:
y=4x+22
There would be 18 books per box.
126/7 = 18
Hope this helps!
Add 21 to both sides, so you get 9z = 81
X = 112
Sorry I had to smoosh the image so it would fit.
I think the answer will be A
