The point slope form of a line is:
point (a,b)
slope: m
equation: (y - b) / (x - a) = m => y - b = m (x - a)
Where m is the slope of the parallel line.
You need to know that parallel lines have the same slope, so m is the slope of both lines.
These are equivalent forms of the equation searched and both are valid answers:
y - b = m (x - a)
y = m (x - a) + b
