[tex]\text{Given that,}\\\\~~~~~~~2x^4 +2y^4 +2z^4 = 144\\\\\implies 2(x^4+y^4 +z^4) = 144\\\\\implies x^4 +y^4 +z^4 = \dfrac{144}{2}\\\\\implies x^4 +y^4 +z^4 = 72\\\\\text{Mean} = \dfrac{x^4+y^4+z^4}{3}\\\\~~~~~~~~=\dfrac{72}{3}\\\\~~~~~~~~=24[/tex]
