Rewrite this equation in the form of y=mx+b

y-3=1/2x+1

we now know that the slope is -2 and since parallel lines have the same slope we know the line we are getting the equation to has a slop of -2. From here there are 2 ways to do this problem we can either use point slope formula or sub in the point and slope into the eqation y=mx+b and solve for b.

Using point slope formula

y-y1=m(x-x1)

where y1=1, x1=3, and m = -2

y-1=-2(x-3)

y=-2x+6+1
y=-2x+7 
using algebra

y=mx+b

where y=1 m=-2 and x=3

1=-2(3)+b
1=-6+b
7=b

y=-2x+7