The slope-intercept form of an equation of a line looks like this:
Where m is the slope and b the y-intercept. Comparing this with our equation:
We can conclude that m=-0.3 and b=43 which means that the answer for the first box in part a is -0.3.
The slope of a linear function tells us how much does y-values increase or decrease when the x-value increases in 1 unit. In our case the x-values represent the years past after 1985 and y the percentage of men smoking cigarettes in a certain city. This means that a slope of -0.3 means that the value of the function (y) decreased by 0.3 per year after 1985. Then the answers for the two boxes in part (b) are decreased and 0.3.