Explanation:
the slope of a line is the ratio "y coordinate change / x coordinate change" when going from one point on the line to another.
when the slope is 0, it means the y coordinate change is 0 for all points. that means y is a constant. and the line is a horizontal line.
to go through (-2, 5) this constant y has to be the y value of the point.
so,
y = 5
that's it. that is the whole equation for that line, because the slope m is 0. what remains is the y-axis intercept (y = 5).