Answer
first blank $\rightarrow \ \ x-(x+3)$
second blank $\rightarrow \ \ -3$
third blank $\rightarrow\ \ -\displaystyle \frac{1}{x(x+3)}$
Work Step by Step
The complex rational expression is multiplied with $\displaystyle \frac{x(x+3)}{x(x+3)}=1$
in order to cancel the fractions in the numerator
After this, the numerator equals $\underbrace{x}_{(x+3)\ cancels} - \underbrace{(x+3)}_{x\ cancels}$
we fill the first blank with $x-(x+3)$
After simplifying the numerator, it equals $-3$. The expression is now
$=-\displaystyle \frac{3}{3x(x+3)}\qquad $... fill the second blank with $-3$.
3 is a common factor, so we reduce (divide both the numerator and denominator) with 3
$=-\displaystyle \frac{1}{x(x+3)}\qquad $... third blank = $-\displaystyle \frac{1}{x(x+3)}$
