Question 363806
x^2/3 - x^1/3 - 20 = 0

Let y = x^1/3

Substitute x^1/3 = y 

y2 - y - 20 = 0

Solve by factoring

(y-5) (y+4) = 0

y-5 = 0

y = 5

Since y = x^1/3
Then x^1/3 = 5

Raise both sides by exponent 3 to get x

      [x^1/3 = 5]^3
          x  = 5*5*5
          x  = 125