Do you mean the slope of the line or the y-intercept
(2002-2001)/(18.75-17.60)= 0.869 =slope
y=mx + b -> 2001= 0.869 (17.60) +b -> b= 1985.7= y-intercept
Bow hello IQR is 21 + 1 -1 = 21
(4,9) is in quarter I and (4,-9) is in quarter IV of the graph. (4,-9) is the point (4,9) reflected over the x-axis. they are similar bc both have 4 as their x coordinate.