First, you must find out what the similarity is between the two triangles to use it as a point of reference for the rest of the equation.
In order to find x, divide 20 by 5, this equals 4. now divide 28 by 4. This equals 7. So x equals 7.
Now we need to find y. The angle of the smaller triangle is 120*. Since the triangles are similar, that means the angle is the same for both triangles. So y equals 120*.
Hope this helps!