Well when you look at equations, they are all built from y=mx+b. Y and x are a point on that line, m is your slope, and b is the y intercept. So when you look at two equations, take the absolute value of m to find which is steeper. Take these two examples.
y=3x+4
y=-7x+4
Take the absolute value of 3 and -7
|3|=3
|-7|=7
7 is the larger number so y=-7x+4 has a steeper slope.