Answer:
Y = 55°
Explanation:
x and 100° are on a straight line and are adjacent angles, sum = 180°, we subtract 100° from 180° and find x, 180° - 100° = 80°. Now knowing that the sum of the interior angles in a triangle is 180° we can find y by subtracting the known angles from 180°. 180 - 80 - 45 = 55° (Y value and your answer).