I got the answer as you can see there but i just dont understand why this applied the formula for rotation about the z axis, how do i know when to apply rotation about x axis or y axis based on this question?

4. This problem works in 2D space using homogeneous coordinates, so all your matrices s should be 3 by 3. [ -3 Let T1 be the translation matrix that translates by , let R be the rotation matrix that rotates by 90 degrees, and let Ty be the translation matrix that translates by 2 31 FIrst, write down these three matrices: C -so 2 O) -a1