i0=0.05; r1=2500;r2=100;r3=200;
NSolve[{3i1+i0==i1+i2,i1+i2==i3,v1-v2==i1*r1,v1-v2==i2*r2,v2-0==i3*r3},{i1,i2,i3,v1,v2}]