def line(coefficients, x):
    """
    For a given value x calculate y = A*x + B.

    Parameters
    ----------
    coefficients : tuple
        A tuple with the line coefficients (A, B).
    x : float
        An argument of a linear equation.

    Returns
    -------
    y : float
        A calculated value of the linear equation.
    """
    return coefficients[0]*x + coefficients[1]