The line with equation y = -2x + 3 has a slope of -2
The line parallel to line with equation y = -2x + 3 has a slope of -2
This is because parallel lines have the same slope
Taking a point (x,y) along the parallel line passing through (-100,-100)
Slope = change in y-axis divide by change in x-axis
-2 = (y - -100) ÷ (x - -100)
-2(x + 100) = y + 100
y = -2x - 300