From the description
[tex] \tan \angle AOB = \frac 4 7[/tex]
[tex] \angle AOB = \arctan \frac 4 7 \approx 29.74^\circ[/tex]
If we rotate so AOA' is straight, that's a 180 degree rotation. So A'OB is the supplement of the above,
[tex] \angle A'OB = 180^\circ - 29.74^\circ = 150.26^\circ [/tex]
Answer (approximately): 150.26 degrees