import math


def pts_to_secs(time_in_seconds: float, time_base: float, start_pts: float) -> float:
    """
    Converts a present time with the given time base and start_pts offset to seconds.

    Returns:
        time_in_seconds (float): The corresponding time in seconds.
    """
    if time_in_seconds == math.inf:
        return math.inf

    return (time_in_seconds - start_pts) * float(time_base)