| Numbers | Answer |

| 1 | 1 |

| 2.3 | 2.3 |

| 3.2, 4.5 | 4.5 |

| 2.3 | 2.3 |

| 3 | 3 |

| 1.1,2.2,3.4 | 3.4 |

'Numbers' header in the above data is in cell A1. The following formula will work based on your sample data:

=MAX(VALUE(TEXTSPLIT(A2,",",,TRUE)))

TEXTSPLIT(A2,",",,TRUE) splits out the numbers across columns wherever there is a comma. VALUE() converts the output of TEXTSPLIT() to numbers. MAX() takes the max number from the array of numbers across the columns.