Answer:
y = -3x +180
Explanation:
It works best if you can identify points that lie at grid intersections. Two of them are ...
(30, 90), (40, 60)
The slope formula give the slope of the line as ...
m = (y2 -y1)/(x2 -x1)
m = (60 -90)/(40 -30) = -30/10 = -3
The slope-intercept equation can be rearranged to help you find the y-intercept:
b = y -mx
b = 90 -(-3)(30) = 180 . . . . using the first point
Then the slope-intercept equation is ...
y = mx +b . . . . . . line with slope m and y-intercept b
y = -3x +180