Answer:
The average was 259.24 in 1996.
Step-by-step explanation:
In order to find the year that the average, "y", is 259.24 we need to apply this value on the given expression, as done below:
[tex]259.24 = 0.15*x + 255.34\\0.15*x = 259.24 - 255.34\\0.15*x =3.9\\x = \frac{3.9}{0.15}\\x = 26[/tex]
The average was 259.24 after 26 years, therefore it was in 1996.