Help, Solve for X

4x^-2/3 = 16

i got to the point where 1/3\sqrt{4x^2} = 16 , then i am totally lost

Also what is the rule for a base with a power of negative fraction? Why do you have to flip ex: x^-1/2. 1/\sqrt{x}

Thank You

PS: am i posting in the corrct subforum？。。.