Answer:
As you should know, the sum of angles of any triangle is 180º, as a quadrilater is two times a triangle, the sum of its angles is 360º
So we know the sum of its angles is 180º and we know there are two angles of 90º, one indicated with a square.
The other two angles measuer x and x - 58, and, if we know that they sum 360, we can do an equation.
90 + 90 + x + (x - 58) = 360
122 + 2x = 360
2x = 360 - 122
2x = 238
x =

x =

Sowe know one angle measueres 119º and the other 61º