Perform the Indicated Operation and Express Your Answer in Simplest $$\frac { n } { n - 3 } + \frac { n + 7 } { n + 7 } + \frac { 16 n + 21 } { n ^ { 2 } + 4 n - 21 }$$

Short Answer

Perform the indicated operation and express your answer in simplest form. $$\frac { n } { n - 3 } + \frac { n + 7 } { n + 7 } + \frac { 16 n + 21 } { n ^ { 2 } + 4 n - 21 }$$ Please enter your answer as one fraction with the denominator factored completely.