The vector can be expressed as (X,Y,Z)=(2y,−z,3x). And if the center of the sphere is (0,0,0) the radius will be expressed as r=OM=(4y^2+z^2+9x^2)^(1/2).By this formula (X,Y,Z)=(rcosθsin,rsinθsin,rcos) you can get the result of theta as arctan(−z/2y) and =arccos(3x/r).Now you can easily substitute the values of theta and phi and solve to get the answer.