The equation of a line describes every point
that is on that line. A point is of the form (x,y). If a
point is on the line X=2 that means that every point on it must start with
two eg (2,3).
Look at each of these lines and try to work out what their equation would be then point to them and the answer will be displayed. 
In order to find the equation of a line you need a point and the slope. then plug into the equation

Worked
Question
The line L has slope 2 and goes thro' the point a(2,3). What is its
equation?
m
= 2 and
a(2,3)
y  y_{1 }= m(x  x_{1})
y  3 = 2(x  2)
y  3 = 2x  4

2x + y = 4 + 3
2x+y=1 Multiply everything by 1
2x  y = 1