def check_answers(answers, answer_key):
    """
    Check students’ answers against answer key.

    Inputs: answers, a tuple of tuples of strs.
            answer_key, a tuple of strs.
    Returns: tuple of tuples of ints.
    """

    def check_section(current, start, end):
        """
        Mark answers in a section.

        Inputs: current, a list of strs.
                start, an int.
                end, an int.
        Returns: an int.
        """
        counter = 0
        for i in range(start, end):
            if current[i] == answer_key[i]:
                counter += 1
        return counter

    final = []
    for elem in answers:
        results = [
            check_section(elem, 0, 12),
            check_section(elem, 12, 24),
            check_section(elem, 24, 36),
            check_section(elem, 36, 47),
            check_section(elem, 47, 57),
            check_section(elem, 57, 71),
        ]
        final.append(tuple(results))
    return tuple(final)