Write an equation in the form y mx b for the average cost y of a textbook x years after 1990 Use the data points 0 38 and 8 86 to find the equation Then use the equation to predict the average cost in 2012 1 y 38x 6 the cost in 2012 is 842 2 y 6x 38 the cost in 2012 is 86 3 y 6x 38 the cost in 2012 is 170 O 4 y y 38x 6 the cost in 2012 is 234