Answer:
The graph of a linear equation is a straight line. The "solution" to a system of two linear equations is the point where the two lines cross. If the two lines are parallel, they never cross; hence parallel lines have no solution. Two lines are parallel if they have the same slope (the m value in y = mx+b). One of your equations is y = -2x + (you left the y-intercept out). The slope is -2. So any line with a slope of m = -2 will be parallel to this line and will not cross it. The second line also needs a different value of b, the y-intercept. Otherwise it is the same line and every point is a solution. So if your equation is:
y = -2x + 1
Then any equation of the form y = -2x + b, b≠1 will create a system with no solution. Hence the values of m and b are m = -2, b ≠ 1.