step 1
Find the slope
we need two points
we take
(0,360) and (18,0)
m=(0-360)/(18-0)
m=-360/18
m=-20
the equation in slope intercept form
y=mx+b
we have
m=-20
b=360
substitute
y=-20x+360
therefore
the slope is negative
m=-20
y-intercept is 360
equation is y=-20x+360