The slope -intercept form of linear equation is y=mx+b.
Where m= slope and b=y-intercept.
Formula to find m is,

The line passes through (6,9) and(4, 17). So, we can plug in x1=6, y1=9, x2=4 and y2=17 in the above formula. So,


So, m=-4
Now we can plug in m=-2, x=6 and y=9 in y=mx+b to get the value of b. So,
9=(-4)*(6)+b
9=-24+b
9+24=b Adding 24 to each sides.
So, b=33.