Answer:
approx. m=-0.467, approx. b= 12.33
Explanation:
** I would recommend you to plug all the points into your TI-nspire and let it give the estimate, but we can also do it by hand I suppose
I would pick (5,10) and (20,3) since they are closest to the geometric center of the upper and bottom part
so let the best-fit line be Number of sweaters Sold = m*T + b
Sub (5,10) and (20,3) into the equation, we get
=> 15m = -7 => m=-7/15 = -0.467
Sub (5,10) back in, we get 5*(-7/15) +b =10 => b= 37/3 = 12.33