The answer is 10 because all the angles are equal making it a equilateral triangle.
Therefore, the sides are all equal to one another, 3x - 8 = 5x - 20.
You just solve for x and get 6. You then plug in 6 for x and evauluate the equation, getting 10.
Don't know if it's right, but do let me know! use percentage to visualise your workings. :)
Y-8=-1/2x + (-2)
+8 +8
y=-1/2x +6
I just used a 2 step equation for it. I first used Distributive Property. Then Subtracted 8 from each side