Answer:
x=81, y=99, z=129
Explanation:
for x, the sum of all angles in a triangle is 180, therefore you just have to add 48 and 51 then subtract the answer from 180.
for y, a strait line is 180 degrees, so you just have to subtract x from 180 to get y.
for z, you have to look at it in a different angle and see that angle 51 and angle z make a strait line, therefore you just have to subtract 51 from 180.