Final answer:
The equation of the horizontal line that passes through point M(-2, 6) is y = 6.
Step-by-step explanation:
The equation of the horizontal line that passes through point M(-2, 6) can be determined by observing that a horizontal line has a slope of 0. Since the line is parallel to the x-axis, the value of y remains constant for all values of x. In this case, since the line passes through point M(-2, 6), the equation of the line is y = 6.