How do you simplify 2 cubed root 81 + 3 cubed root 24?
The answer is
Look at the values whose cube roots are involved in the problem and determine whether they are perfect cubes or whether they contain factors which are perfect cubes (24 is 3 x 8, and 8 is a perfect cube, and 81 is 3 x 27; 27 is a perfect cube).
This allows you to simplify the problem as shown here:
This step is true because
I've put in some brackets in the hope of keeping this clear.