9y-1=y-25 and with work? is really confusing me.

x = -3

Step-by-step explanation:

First Subtract the lowest variable which would be "y" from 9y. 9y changes to 8y and y cancels out, bring everything else down. the equation is now 8y-1=-25. Now add positive one to both sides -25 becomes -24 and -1 cancels out. the equation is now 8y=-24. -24 divided by 8 equals -3 and the 8y cancels out. the equation is now x equals -3.

Exterior angles are always supplementary to the interior angle, because to get an exterior angle you have to keep the line going from one interior angle. That means that 

(measure of interior angle)+(measure of exterior angle)=180 degrees

You can change the form of the equation and get

(measure of exterior angle)=180 degrees - (measure of interior angle)

So, to find the exterior angle, just subtract the interior angle from 180.

Hope this helps!