Line gh passes through points (2, 5) and (6, 9). which equation represents line gh?

y = x + 3
y = x – 3
y = 3x + 3
y = 3x – 3

The answer
the main rules concerning such a problem is as follow:
let be D a line that the equation is  ax+by+c =0, if a point A(a1, a2) passes through D, so the coordinates of A verifies the equation of D.
that means, aa1 +ba2 +c =0
in our case, Line GH passes through points (2, 5) and (6, 9), therefore these two points must verify the equation of GH
the answer is 
y = x + 3
proof, when x = 2, y = 2+3=5,   Line GH passes through points (2, 5)
          when x =6, y = 6 +3 =9, Line GH passes through points (6, 9)