Find All Values of X Satisfying the Given Conditions $y _ { 1 } = \frac { 1 } { x + 6 } , y _ { 2 } = \frac { 2 } { x + 3 } , y _ { 3 } = \frac { - 3 } { x ^ { 2 } + 9 x + 18 }$

Multiple Choice

Find all values of x satisfying the given conditions.
- $y _ { 1 } = \frac { 1 } { x + 6 } , y _ { 2 } = \frac { 2 } { x + 3 } , y _ { 3 } = \frac { - 3 } { x ^ { 2 } + 9 x + 18 }$ , and $y _ { 1 } + y _ { 2 } = y _ { 3 }$

A) $\{ 0 \}$
B) $\{ - 6 \}$
C) $\{ 3 \}$
D) $\varnothing$