Answer:
y = 9
Explanation:
Both points are on the same horizontal line:
y = 9
_____
The first step in problem solving is to look at the information you are given. If you want to skip that step, and go straight to the procedure for finding the equation of a line through two point, here it is:
The slope is given by ...
m = (y2 -y1)/(x2 -x1)
m = (9 -9)/(7 -5) = 0/2 = 0 . . . . . . . tells you the line is horizontal
The y-intercept is given by ...
b = y1 -m·x1
b = 9 -0·5 = 9
Then the equation of the line is ...
y = mx +b
y = 0·x +9
Simplifying gives ...
y = 9
__
Additional comment
The equation for a horizontal line is y = constant.
The equation for a vertical line is x = constant. A vertical line will not have a unique y-intercept. It will be the entire y-axis if it is x=0.