Question 709448
{{{5x^(2/3)=20}}}

{{{x^(2/3)=4}}} Cubed both sides and get:

{{{(x^(2/3))^3=4^3}}} Simplify

{{{x^2=4.4^2}}}  Take the square root for both sides

{{{x=8}}}  Check: {{{5.8^(2/3)-4=16}}} -> {{{5.4-4=16}}} -> {{{20-4=16}}}