To solve this remember PEMDAS (Parenthesis, Exponents, Multiplication, Division, Addition, Subtraction). This is the order in which you solve such problems.
So, start with P or Parenthesis. The brackets ([]) are considered parenthesis, which means you want to solve everything inside them first. So to simplify inside the brackets, think pemdas again and look for more Parenthesis. There are two sets of parenthesis inside the brackets, but only one requires you to simplify: (-2-5) [aka (-2)+(-5).] which is -7.
This leaves you with -2[(-3)(-7)(3)]
Next comes E, but there are no exponents.
After that is Multiplication. You can now multiply the numbers in these>> [] brackets. So (-3) x (-7) x (3) is 63. the number is positive because the two negatives cancel one another out to become positive.
that leaves you with -2[63] which is equal to -126.
I hope this helps :)
