So a straight line is always equal to 180 degrees. So, to find the length of the inner angle, subtract 100 from 180= 80. Now that you've gotten the value of that angle, you'll have to find x and y. All angles of a triangle add up to 180 degrees. 180-80= 100. The small dash on both of those lines means they are equal. Do 100/2 = 50. Hope this helps!
