The equation of Mandy's regression line for the given paired data set is y = -2x + 13.
Calculate the slope (m):
To find the slope, we can use the formula:
, where
and
are two points on the line.
Using the given points (2,9) and (4,5), we have:

Substitute the slope and one of the given points into the equation:
We can use either point (2,9) or (4,5) in the equation y = mx + b.
Using point (2,9):
9 = -2(2) + b
Simplifying the equation, we get:
9 = -4 + b
b = 9 + 4 = 13
Write the equation of the regression line:
Now that we have the slope (m = -2) and the y-intercept (b = 13), we can write the equation of Mandy's regression line:
y = -2x + 13