Answer:
See below.
Explanation:
I'll work it out myself, then we should be able to see the mistake:-
6 ∛ (64x^5y^9)
= 6 * 4 * x^(5/3) * y^3
= 24 x^(3/3) * x^(2/3) y^3
= 24 x y^3 ∛(x^2)
You've got confused withe the cube root (∛) on the first line. You've interpreted it as ' 3 times the square root' so you were on the wrong road from the beginning.
Note that y^9 has cube root y^(9/ 3) = y^3 and x^5 has cube root of x^(5/3). The square root of x^9 is x^(9/2).