4931.sagews

var('x1 x2 x3 y1 y2 y3 z1 z2 z3 r1 r2 r3 x y z')

(x1, x2, x3, y1, y2, y3, z1, z2, z3, r1, r2, r3, x, y, z)

eq1 = (x-x1)^2+(y-y1)^2+(z-z1)^2==r1^2

eq2 = (x-x2)^2+(y-y2)^2+(z-z2)^2==r2^2

eq3 = (x-x3)^2+(y-y3)^2+(z-z3)^2==r3^2

solve([eq1,eq2,eq3], x, y, z)