First, solve the given equation for y:
2x + y = 9
y = -2x + 9
the slope of the equation is m =-2.
Now, consider that all parallel lines have the same slope, then, the slope of the required line is m = -2.
Next, use the following general equation for a line:
y - yo = m(x - xo)
where (xo,yo) is any point on the line. Replace (xo,yo) = (-1,6) with m=-2 into the previous equation and solve for y:
y - 6 = -2(x - (-1))
y - 6 = -2x - 2
y = -2x - 2 + 6
y = -2x + 4
Hence, the equation of the line which crosses through the point (-1,6) and parallel to 2x + y = 9 is y = -2x + 4