- The average annual number of cigarettes smoked by an adult in some countries continues to decline. For the years 1997-2006, the equation y = -49.6x + 1756.7 approximates this data. Here x, is the number of years after 1997 and y is the average annual number of cigarettes smoked. If this trend continues, find the year in which the average number of cigarettes smoked is zero. To do this, let y = 0 and
solve for x.