\[ \boxed { \sin \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) +{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -x=0} \]
Mathematica: cpu = 0.010001 (sec), leaf count = 19 \[ \text {DSolve}\left [y'(x)+\sin \left (y'(x)\right )-x=0,y(x),x\right ] \]
Maple: cpu = 0.031 (sec), leaf count = 16 \[ \left \{ y \left ( x \right ) =\int \!{\it RootOf} \left ( {\it \_Z}+\sin \left ( {\it \_Z} \right ) -x \right ) \,{\rm d}x+{\it \_C1} \right \} \]