The answer should be - 10.
Y = - 10x + 5 is presented in the slope-intercept form. Also known as y = mx + c. M is the slope, and c is the place (y value) where the line cuts at the y-axis.
Remember that 2 parallel lines must have the same slope with each other.
Therefore, since m is the slope and the line is parallel to each other, the answer should be - 10, just answer with the number in the place m of the equation of straight line.