The trend line of a company's output is $y = 120 + 8x$, with $x = 0$ at 2020 and $x$ in years. What does the 8 tell us?

Explanation

1. 01

   In $y = a + bx$, $b$ is the change in the trend value when $x$ goes up by 1, that is per year.

2. 02

   So the trend output rises by 8 units a year; the 120 is the trend value for 2020.