I would like to take the results of `Fit` (or any `FittedModel`) and treat them as text, including making substitutions for the variables. But I can't figure out how to do this.

For example

```
"Subscript[I, m]/Subscript[I, r]" <> " = " <> ToString[Fit[currentRatio[32],{1,x,x^2,x^3},x]/.x->"Subscript[I, r]"]

```

produces the garbled output

```
Subscript[I, m]/Subscript[I, r] =                                      -6   2             -10   3
0.591585 + 0.00126235 I  - 1.75804 10   I   + 8.08979 10    I
                       r                 r                   r

```

How do I treat the results of `Fit` or `FittedModel` as text?