Answer:
use the formula for a line through two points
[tex]y - y_{1} = \frac{y_{2} - y_{1}}{x_{2} - x_{1}} \times (x - x_{1})[/tex]
plug in the given points:
[tex]y - 7 = \frac{15 - 7}{5 - 1} \times (x - 1)[/tex]
[tex]y = \frac{8}{4} \times (x - 1) + 7[/tex]
[tex]y = 2 \times (x - 1) + 7 \\ y = 2x - 2 + 7 \\ y = 2x + 5[/tex]
