Answer:
y = -3x +7
Explanation:
The equation for a line is: y = mx + b
m = slope
x = the x-value
y = the y-value
b = the y-intercept
Since the y-intercept is 7, we know the first part of the equation is: y = mx +7
Also, since the line is decreasing from right to left, m is going to be negative. A way to calculate the m is rise/run. Count how many blocks it is going horizontally (run)and how many blocks it is increasing/decreasing when going to the right (rise). Then divided the "rise" over "run". Another way is to choose two points. Now use the equation y1-y2/x1-x2,
or y2-y1/x2-x1. I am going to show using the equation.
My two points are (0,7) and (2,1)
change in y (rise):7-1 = 6
change in x (run): 0-2 = -2
6/-2 = -3. Your slope is -3. Now lets put it all together.
y = -3x +7
You can see that for every square moved to the right ONCE the y value is decreasing by 3 each time.