✓ Mathematica : cpu = 0.0129444 (sec), leaf count = 29
DSolve[{t^2*(1 - Sin[t])*Derivative[1][x][t] == t*(1 - 2*Sin[t])*x[t] + t^2*y[t], t^2*(1 - Sin[t])*Derivative[1][y][t] == (t*Cos[t] - Sin[t])*x[t] + t*(1 - t*Cos[t])*y[t]},{x[t], y[t]},t]
✓ Maple : cpu = 0.068 (sec), leaf count = 23
dsolve({t^2*(1-sin(t))*diff(x(t),t) = t*(1-2*sin(t))*x(t)+t^2*y(t), t^2*(1-sin(t))*diff(y(t),t) = (t*cos(t)-sin(t))*x(t)+t*(1-t*cos(t))*y(t)})