The answer you selected is incorrect.

Chips | Fries | Total | |

Roast Beef Sandwich | 9 | 13 | 22 |

Turkey Sandwich | 14 | 11 | 25 |

Total | 23 | 24 | 47 |

To answer this question we have to recognize that we are only looking at the individuals who ordered a roast beef sandwich. So, our sample space is only 22. 13 individuals ordered fries with their roast beef sandwich so the probability is , which is choice B.

This is an example of conditional probability. For a video about conditional probability click here.

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