Answer:
[tex] \frac{y - 18}{x - 1} = \frac{23 - 18}{1.5 - 1} = \frac{5}{0.5} = 10 \\ y - 18 = 10(x - 1) = 10x - 10 \\ y = 10x + 18 - 10 = 10x + 8 \\ \boxed{f(x) = 10x + 8}[/tex]
hope this helps.