The slope of the side AC is [tex]\frac{3-7}{3-5}=-2[/tex], so the slope of the altitude is the negative reciprocal, 1/2.
Substituting into point-slope form,
[tex]y+1=\frac{1}{2}(x-11)\\\\y+1=\frac{1}{2}x-\frac{11}{2}\\\\\boxed{y=\frac{1}{2}x-\frac{13}{2}}[/tex]