Question 508881
We have a line that is horizontal and it follows that its slope is 0. This means that a line parallel to this line also has slope 0 and is in fact a horizontal line.  We will expect that this line will be of the form  y = (some number). And since our coordinate is (5,1) [implying that y = 1], a good guess would be that the line is y =1. Let's solve this algebraically.

We have a slope and we have a point. Let's use point-slope form.

y - y1 = m(x-x1)

y - 1 = 0(x-5)

y - 1 = 0

y = 1 <--- Just as we expected.