Question

What is the slope of the line y=3

Answer 1

The slope intercept form of the line is:

y=mx+b, where m=slope and b=y-intercept

In this case y is equal to a constant, which is also the y-intercept and is of the form:

y=k

Note that there is no mx part to that line, so for all values of x, y=3.  And the only value for m that would make mx=0 is for m=0

Since m=0, there is a slope of zero.  This is just a horizontal line.