"Ah, now I see!" said the blind man.
You got it! (I've edited the original post to insert the missing formatting tags.)
is what the book says is correct.
I say this is as correct
They're exactly the same thing, just arranged a little differently. Since multiplying by one-fifth is the same as dividing by five, either form should be fine.
but isn't this: y=2-.4x, simpler yet?
Generally, books and teachers prefer the fractional form. But your decimal form should
be acceptable since, as you point out, it is the same.