We begin by rearranging the triangles.
In the first triangle:
x+66+90=180
x+156=180
x=180-156
x=24
In the second triangle
y+90+24=180
y+114=180
y=180-114
y=66
Note: Similar triangles are the same shape, but not necessarily the same size.
We see that the angles in both triangles are exactly the same.
We conclude that the triangles are similar.