To find the slope of the line that passes through the points (7, 4) and (-10, 4), we need to apply the next formula:

Then, we have to label those points as follows:
(7, 4) ----> x1 = 7, y1 = 4
(-10, 4) ---> x2 = -10, y2 = 4
Then, we have:

Therefore, the slope is equal to zero, m = 0. It means that the line is a horizontal line.
In summary:
Slope = 0