Let calculate the slope
[tex]M=\frac{y2-y1}{x2-x1}=\frac{4-5}{9-7}[/tex]So,
[tex]M=-\frac{1}{2}[/tex]Now for b
[tex]b=y-Mx[/tex]Using (7,5),
[tex]b=5+\frac{1}{2}(7)\rightarrow b=\frac{17}{2}[/tex]The equation of the line that passes through the points
[tex]y=-\frac{1}{2}x+\frac{17}{2}[/tex]