Because the sides are equal, the triangles are isosceles.
From statement one:
Angle RQS = Angle RSQ --> label this Angle a
From statement two:
Angle TSU = Angle TUS --> label this Angle b
You know the following:
1.) a+b+x=180 (they form a straight line)
2.) (180-a)+(180-b)+x+90=360 (interior angles of a quad.); Simplify: -a-b+x=-90
Combine the two:
a+b+x-a-b+x=180-90
2x=90
x=45.