Use the Five-Step Strategy for Solving Word Problems to Find $y _ { 1 } = \frac { 1 } { x + 7 } , y _ { 2 } = \frac { 1 } { x + 4 } , y _ { 3 } = \frac { - 3 } { x ^ { 2 } + 11 x + 28 }$

Multiple Choice

Use the five-step strategy for solving word problems to find the number or numbers described in the following
exercise.
- $y _ { 1 } = \frac { 1 } { x + 7 } , y _ { 2 } = \frac { 1 } { x + 4 } , y _ { 3 } = \frac { - 3 } { x ^ { 2 } + 11 x + 28 }$ , and the sum of $y _ { 1 }$ and 3 times $y _ { 2 }$ is $y _ { 3 }$ .

A) $\{ 0 \}$
B) $\{ - 7 \}$
C) $\{ 4 \}$
D) $\varnothing$