The angles in each of those 3 similar tirangles are 66,60 and 54
The 3 triangles are similar so their angles are 66,60 and 54
angle MNO must be 54 so that MNO can be 60
which means that angle NRO must be 60 degrees
It would be better to do formal solution though.
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NOTE: I am editing because it mostly disappeared when I published. How annoying.
I have not seen that compilation error for a long time.