cube root (3*3*3*4*a^9*a*b^12)
Since it is a cube root(3), there is a match of 3 3's so a 3 can come outside the radical.
divide the index 3 into the power 9 on the a and a^3 can come out of the radical.
divide the index 3 into the power 12 on the b and b^4 can come out of the radical.
3a^3b^4 cube root(4a)