H = 3a + 28.6
A pediatrician uses the model above to estimate the
height h of a boy, in inches, in terms of the boy's
age a, in years, between the ages of 2 and 5. Based
on the model, what is the estimated increase, in
inches, of a boy's height each year?

A) 3
B) 5.7
C) 9.5
D) 14.3

Where m is the slope of the line and b is the y-intercept of the line, or the y-coordinate of the point at which the line crosses the y-axis. to write an equation in slope-intercept form, given a graph of that equation, pick two points on the line and use them to find the slope. this is the value of m in the equation.