Y=78 A polygon has a total of 5 interior angles In order to find the total amount of angles in a shape you do (the amount of angles - 2)x180 degrees (5-2(3))180 3x180=540 Add the numbers you know (10+20+30+40+50=150) 540-150=390 and there are 5y altogether so divide 390 by 5 which is 78
