Firstly, we need to compare the information ew have from both sides of the equation, the denominators.
The different between the denominator is that the right side has the factor (w + 6), while the lest side does not.
So, sstarting from the expression on the left side, we can introduce the factor (w + 6) into the denominator by multiplying both the numerator and the denominator by this factor:
The order of the factor dont change the result, so we can switch the factors on the denominator to get:
Now, by comparison, we can see that the blank part is the following: