Let's represent the given (length, years) as (x, y)
at time 0 year, the glacier is 1000 meters
at time 15 years, the glacier retreated 255 meters and that's 1000 - 255 = 745
so we have the points (0, 1000) and (15, 745)
Using the slope formula :
[tex]m=\frac{y_2-y_1_{}}{x_2-x_1}[/tex]where m represents the average annual rate of retreat.
[tex]m=\frac{745-1000}{15-0}=\frac{-255}{15}=-17[/tex]The average annual rate of retreat of the glacier is 17 meters per year
