10 if you look at those three angles, they form a triangle so you just have to remember that the three angles in a triangle always add up to 180°
11 Angle 11 and angle 4 are opposite interior angles; therefore they are congruent. Combine this with the logic in number 10 and the three angles add up to 180° again
12 By looking at the diagram and examining these angles they form a circle. To solve this all you have to remember is the number of degrees in a circle which is 360°. (Some people may look at this and realize that three angles formed a straight angle which would be 180° the opposite three angles also for a straight angle 180° so therefore the two added together was still 360°)
