\[ y^{(3)}(x) (x+\sin (x))+3 (\cos (x)+1) y''(x)-3 \sin (x) y'(x)-y(x) \cos (x)+\sin (x)=0 \] ✓ Mathematica : cpu = 0.0844902 (sec), leaf count = 47
DSolve[Sin[x] - Cos[x]*y[x] - 3*Sin[x]*Derivative[1][y][x] + 3*(1 + Cos[x])*Derivative[2][y][x] + (x + Sin[x])*Derivative[3][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to \frac {c_3 x^2}{x+\sin (x)}-\frac {\cos (x)}{x+\sin (x)}+\frac {c_2 x}{x+\sin (x)}+\frac {c_1}{x+\sin (x)}\right \}\right \}\] ✓ Maple : cpu = 0.091 (sec), leaf count = 25
dsolve((sin(x)+x)*diff(diff(diff(y(x),x),x),x)+3*(cos(x)+1)*diff(diff(y(x),x),x)-3*sin(x)*diff(y(x),x)-y(x)*cos(x)+sin(x)=0,y(x))
\[y \left (x \right ) = \frac {c_{3}+c_{1} x^{2}+x c_{2}-\cos \left (x \right )}{\sin \left (x \right )+x}\]