How should this sentence be punctuated Frances called in sick but back tomorrow?

Here are a few ways to punctuate that sentence, along with explanations:

1. With a comma:

* Frances called in sick, but she'll be back tomorrow. (This is the most common and natural way to punctuate this sentence.)

2. With a semicolon:

* Frances called in sick; she'll be back tomorrow. (This emphasizes the contrast between being sick and returning to work.)

3. With a colon:

* Frances called in sick: she'll be back tomorrow. (This emphasizes the explanation following the first part of the sentence.)

4. With a dash:

* Frances called in sick—she'll be back tomorrow. (This creates a dramatic pause, emphasizing the return to work.)

The best choice depends on the emphasis you want to make and the overall tone of your writing.