Question 6802
Simplify 4[6-4(x-y)+6x]-16y
You evaluate exponents and radicals first. There are none. Whew!
Next, evaluate groups. There are two groups. One is contained in the other. That's why the different type of bracketing was used. It need not have been, however. I like to evaluate the contained groups first, so I would do 
-4(x-y) first, giving -4x + 4y.
The expression then becomes
4[6-4x+4y+6x]-16y.
The other group, 4[6-4x+4y+6x], gives 24-16x+16y+24x.
The entire expression is now 24-16x+16y+24x-16y.
Addition and subtraction always done last, giving
24 + 8x.
Of course, to complete the simplification you would factor out a common value of 8, giving
8(3+x).