Solve the Equation: Finding the Missing Number in ?:(-6)+[-2(94-73)]=-153

Fill in the missing number:

$?\colon(-6)+\lbrack-2(94-73)\rbrack=-153$

We begin by solving the innermost parentheses:

$94-73=21$

We obtain the following calculation:

$x\colon(-6)+\lbrack-2(21)\rbrack=-153$

Next we focus on the parentheses and multiply:

$-2\times21=-42$

We obtain the following calculation:

$x\colon(-6)+(-42)=-153$

Let's consider the multiplication between minus and plus:

$x\colon(-6)-42=-153$

We swap sections:

$x\colon(-6)=-153+42$

$x\colon(-6)=-111$

$\frac{x}{-6}=-111$

Lastly we multiply by minus 6:

$x=-111\times-6=666$