√(- 9 ) / (( 4 - 7 i ) - ( 6 - 6 i )) = 3 i / ( 4 - 7 i - 6 + 6 i ) =
= 3 i / ( - 2 - i ) = - 3 i / ( 2 + i ) =

=
- 1 - 2 i
EXPLANATION
Let's see the facts:
$Sandwiches= 3*$Salads
Bill = $24.92
We can represent this in an equation:
Total Bill = Sandwiches + Salads
Let's call to Sandwiches "x" to Salads "y" and to Bill "B"
Then, the equation will be:
B = x+y = (3*y) + y
Applying distributive property:
24.92 = 3y + y
Adding similar terms:
24.92 = 4y
Dividing both sides by 4:
6.23 = y
Switching:
y=6.23
As we know, y variable represent the salads cost, so:
Answer is $6.23.
The trick is to exploit the difference of squares formula,

Set a = √8 and b = √6, so that a + b is the expression in the denominator. Multiply by its conjugate a - b:

Whatever you do to the denominator, you have to do to the numerator too. So

Expand the numerator:






So we have

But √12 = √(3•4) = 2√3, so

The answer to the question