Wolfram format for mathmatics equations

Question

I am trying to solve a system of 4 equations in Wolfram.

x4 - x1 + x2 - x1 - b - b x1 =0 , x1 -x2+x3-x2 - b- b x2=0 , x1 -x4+x3-x4 + b - b* x4=0, x4 -x3+x2-x3 - b -b* x3=0 , b > 0, solve for{x1,x2,x3,x4}

but it keeps giving me error