When you're given a parallel line, that means you know that both lines should have the same slope m.
And you're given a point (x,y) so you plug in the x for
in the equation and y for 
in the equation.
Also plug in m because that was given.
y - = m(x - )
Then you can simplify the equation to get y = mx + b
And you're given a point (x,y) so you plug in the x for
Also plug in m because that was given.
y -
Then you can simplify the equation to get y = mx + b