Find the equation of a line that has a slope of m=-2 and goes through the point (4,-5)

All you have to do is plug the given information into the formula for point-slope form

y - y1 = m(x - x1)

y + 5 = -2(x - 4)

and that's the equation. if they want it in y = mx + b, however, then you have to take a few extra steps and isolate the y variable.