Remember that the point-slope form of a line is:
[tex]y-k=m(x-h)[/tex]For a line with slope m and that passes through point (h,k)
Now, let's work on the line we're given. SInce the x-intercept is 6, we know that the line passes through (6,0).
Let's calculate the slope m :
[tex]m=\frac{3-0}{5-6}\rightarrow m=\frac{3}{-1}\Rightarrow m=-3[/tex]Now, using point (5,3) we can get the following point-slope form for the line:
[tex]y-3=-3(x-5)[/tex]