Explanation:
at the beginning it is in quadrant III.
that means in the bottom left quadrant (where all x and all y are negative).
the reflection over the x-axis brings it up into quadrant II (upper left quadrant).
the line y = x is the line that goes like a 45° diagonal from the bottom left to the top right.
when reflecting our figure over this line, it brings it from quadrant II into quadrant IV (the bottom right quadrant).
and now, a 90° clockwise rotation moves it by one quadrant in clockwise direction. that brings it back into quadrant III.