Both the triangles shown in the image have one right angle each, which are congruent (because all right angles are congruent).
Again, both the triangles have one angle out of a pair of vertically opposite angles, which must be equal in measure.
Therefore, the two triangles are similar (AA postulate).
So, the remaining angle, in each case, must be equal in measure.
That means 2x=50
`rArr` x=25 degreees.