Question

8x{[(7+4)x2] - [(11-7)x4]}

Answer 1

PEMDAS
P - Parentheses (or other grouping symbols)
E - Exponents 
M - Multiplication
D - Division
A - Addition
S - Subtraction

$8x[(7+4)x^2] - [(11-7)x^4]\\ \\ 8x[(11)x^2] - [(4)x^4] \\ \\ 8x[11x^2] - [4x^4] \\ \\ 88x^3 - 4x^4 \\ \\ -4x^4+88x^3$

If you then want to go on to factor it, your answer would be $-4x^3(x-22)$

Answer 2

For this case we have the following expression:

8x {[(7 + 4) x ^ 2] - [(11-7) x ^ 4]}

First, we solve the parentheses:

8x {[(11) x ^ 2] - [(4) x ^ 4]}

We now resolve the brackets:

8x {[11x ^ 2] - [4x ^ 4]}

We now solve the keys:

8x {11x ^ 2 - 4x ^ 4}

We apply the distributive property:

$88x ^ 3 - 32x ^ 5$

Answer:

$88x ^ 3 - 32x ^ 5$