A straight-line trend, with $x$ in years from 2022, gives trend values 50 for 2020 and 66 for 2024. What is its equation?

Explanation

1. 01

   At 2020, $x = -2$: $a - 2b = 50$. At 2024, $x = 2$: $a + 2b = 66$.

2. 02

   Adding: $a = 58$; subtracting: $4b = 16$, so $b = 4$.