The estimated value of the Mona Lisa was about $100 million in 1960. By the year 2000 its value had increased to approximately $600 million. Write a straight line appreciation equation for the painting where y is the approximate value in millions of dollars and x represents the number of years after 1960.

slope: (600-100)/(2000-1960) = 12.5

Since 1960 is x=0,

y = 12.5x