I came across this problem recently where
$A:b = C:A$ and $B= -9$ and $C = -4$
What is $A$ then?
I got $A^2 = 36$ $\Rightarrow$ $A= \pm 6$
However, as far as my knowledge goes a ratio is always positive
Therefore, we could easily eliminate $A=+6$ and the answer remains $A=-6$
Is my explanation correct, if not then why so? Can -ve Ratios exist?