Given two points (x₁, y₁) and (x₂, y₂), the slope of the line that passes through these two points can be calculated using the formula:

Using an arbitrary point of the line (x₀, y₀), the slope-point form of the line equation is:

Now, from the problem:
(a)

Using (1) to find the slope of the line:

Now, using (1, 9) and (2):

The equation of the line is y = 9
(c)

Using (1) to find the slope of the line:

Now, using (4.2, 7.6) and (2):

Rounding to two decimal places:
