Afamily built a house in a beach resort area. in 1990, the house was 430 ft from the water. with erosion, the house was 400 ft from the water in 2000. assuming a linear relationship between the number of years x since 1990 and the distance y of the house from the water, write an equation for y as a function of x.

We develop an equation for the given situation by first writing the general equation for lines,
                                 y = mx + b
Substituting to this given the values given above,
 (1990)                      430 = b
 (2000)                      400 = m(10) + 430
The value of m from the equation in 2000 is -3. Thus, the equation of that relates the variables is,
                               y = -3x + 430