Answer:
x²¹ /64
Explanation:
To know the mistake made by Javier, let us simplify the given expression. This can be obtained as follow:
(20x / 5x⁸)¯³ = (20x)¯³ / (5x⁸)¯³
= (5x⁸)³ / (20x)³
= 5³x²⁴ / 20³x³
= 125x²⁴ /8000x³
= 125x²⁴ ÷ 8000x³
Recall
Mᵃ ÷ Mᵇ = Mᵃ¯ᵇ
Therefore,
125x²⁴ ÷ 8000x³ = (125/8000)x²⁴¯³
= (1/64) x²¹ = x²¹/64
Thus,
(20x / 5x⁸)¯³ = x²¹/64