x = 81 degrees (The sum of a triangle's angles must be 180 degrees. 48 + 51 = 99, and 180 - 99 = 81)
y = 99 degrees (Y and X are on a supplementary angle. Like a triangle, a supplementary angle's angles must add up to 180 degrees. 180 - 81 = 99)
z = 129 degrees (Z and the 51 degree angle are also on a vertical angle. 180 - 51 = 129)
Hope this helps!
