Part 1
we take the points
(3,1) and (6,2)
find the slope
m=(2-1)/(6-3)
m=1/3
the equation in slope intercept form
y=mx+b
we have
m=1/3
point (3,1)
substitute
1=(1/3)(3)+b
1=1+b
b=0
therefore
y=(1/3)x
Part 2
take the points (8,4) and (9,5)
slope
m=(5-4)/(9-8)
m=1/1
m=1
y=mx+b
we have
m=1
point (8,4)
4=(1)(8)+b
b=4-8
b=-4
therefore
y=x-4