15x + y = 20 in function form

No

Step-by-step explanation:

An equation written in function form begins with f (x)

[or another letter like g (x) or h (x).] It's read "f of x" or "f at x".

f (x) replaces "y" in an equation.

If you want to write 15x + y = 20 in function form, isolate "y" then replace it with f (x).

15x + y = 20

y = 20 - 15x

f (x) = 20 - 15x