def z(j, k):
    """Calculates equivalence scale. z(2,1) is the equivalence scale for a household with two adults and one child

    Parameters
    ----------
    j : float
        the number of adults in the household.
    k : float
        the number of children (under 18 years old).

    Returns
    -------
    type
        float

    """
    return (j + 0.7* k)**0.75