Which regression equation of a line most closely matches the data set? yˆ=1.13x−14.69 yˆ=0.32x−5.89 yˆ=0.59x+3.29 yˆ=3.1x+18.6 x y 4 30 6 38 8 44 10 50 12 55?

The average of the last two points is
  ((10, 50) +(12, 55))/2 = (22/2, 105/2) = (11, 52.5)
Then the slope between this average point and the first point is
  (difference in y-values)/(difference in x-values) = (52.5 - 30)/(11 - 4)
  = 22.5/7 ≈ 3.2

The only choice with a slope near 3.2 is the last one, ...
  y = 3.1x+18.6

A graphing calculator confirms this choice.

20y5 times 2 is 1010 times -2 is -20, plus y