You got four equations with four unknowns. Try to substitute one into another to eliminate the unknowns one by one.

BTW, notice that your x, y, z in f() and in g() are not exactly the same. You'll need to fix this mistake to get the answer correctly.

Quote

"f(x,y,z) = volume of the rectangular paralelpiped=x*y*z where x=length(l}, y=width(w), z=height(h) of rectangular parallelpiped"

 

x,y,z is given to you as terms that define the ellipsoid.

How about you try to define the volume.. centered.. within what is given -- the ellipsoid?