def isNum(s) -> bool:
    """
    Checks if its a number
    >>> isNum("1")
    True
    >>> isNum("-1.2")
    True
    >>> isNum("1/2")
    True
    >>> isNum("3.9/2")
    True
    >>> isNum("3.9/2.8")
    True
    >>> isNum("jazz hands///...")
    False
    """
    if "/" in str(s):
        s = s.replace("/", "", 1)
        s = s.replace(".", "", 1)
    num = True
    try:
        complex(s)
    except ValueError:
        num = False
    return num