In order to find out what the blank of your expression is,, we must solve for y. We can start doing this by distributing -2 through the parenthesis.
y - 4 = -2x - 6
Now you need to move the constant to the right side and change its sign.
y = -2x - 6 + 4
Calculate the sum of -6 + 4.
y = -2x - 2
Since we cannot simplify this down any further,, y is going to equal -2x - 2.
Let me know if you have any further questions.
:)