I have this circuit

I have to find Va and Vb, when i tried to do so, using node analysis I had the Equation Va/6 + (Va-12)/3+(Va-Vb)/5 - 6 - 2=0 and Vb/22+(Vb-20)/4+(Vb-Va)/5 +2 -3=0. Solving simultaneously, i got Va = 23.29V and Vb=21.51V. When I simulated it using Circuit simulator applet, the simulation says that Va = 24.4V and Vb is 25.4V. Can someone point out where did I go wrong? Thanks!