Answer:Step-by-step explanation:You should know your interior/ exterior angles as well as vertical angles and corresponding angles for this. if that's unfamiliar I can explain .10) You have two parallel sides, AB and DC. If you pretend that they went on forever like lines, you would have BC as the transversal. With this you would get angles B and C as interior angles. Specifically consecutive interior angles, so they should add up to 180. With that you solve x + x - 50 = 180. Once you find x angles B and C will be easy.Once you find those two angles you need to know quadrilaterals have an angle sum of 360, and since you will then know three of the angles, since you know angle D is 90, you will be able to find angle A with 90 - (B + C + D). A hint though, you already know B + C is 180 and D is 90.11) You can use the same kind of thinking as 10 here. AB or DC will be the transversal here. Witht hat you know 5x + 4x = 180. Do let me know if there's something you don't understand.12) here you can clearly see x+y = 180, since together they make a straight line. then we have another transversal going through two parallel lines. Not labeled, but the line with the arrows at either end is the transversal we will be using. With this we see the angle with measure x and the angle with measure 3y are corresponding angles. So x = 3y. Well if x = 3y then x+y = 3y + y = 4y = 180. This way you can find y and then plug that in to find x.Hopefully I explained that clearly enough, but again, let me know if I did not.