wolfram alpha - Solve system of equations

Are there any good resources for solving systems of equations out there?

I tried to put this into wolfram alpha, but it doesn´t seem to work:

 solve
 [

   {
    x+a=s+p,
    y+b=q+t, 
    (x^2+y^2)^(1/2)+(a^2+b^2)^(1/2)=(s^2+t^2)^(1/2)+(p^2+q^2)^(1/2),
    x^2+y^2+a^2+b^2=(4/5)*(s^2+t^2+p^2+q^2)
   },
   {s, t, p, q}
 ]

Is there something wrong with the syntax?