The inclination of the lines in the coordinate system is given by their slopes, so to determine which line is steeper you have to compare the absolute values of both slopes.
The first equation y=2 has no slope, if you draw it you will see that for any value of x, y doesn't change, it is always 2.
You can also say that the slope of this equation is equal to zero.
For the second equation y=-7/3x-5, the slope is equal to -7/3.
The second equation is steeper than the first one since the absolute value of its slope is greater.