y = - 2x + 12
the equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y-intercept )
y = - 2x + 7 is in this form with slope m = - 2
Parallel lines have equal slopes, thus
y = - 2x + c is the partial equation.
To find c, substitute (3, 6 ) into the partial equation
6 = - 6 + c ⇒ c = 6 + 6 = 12
y = - 2x + 12 ← equation of parallel line