We are asked to determine the equation of a line that passes through (9,4) and has slope 0. To that let's remember the general equation for a line:

Where "m" is the slope and "b" the y-intercept. Since m = 0, replacing in the equation we get:

Now we replace the point (x,y) = (9,4)

Replacing the value of "b = 4":

And thus we get the equation of the line.