def lin_interpol(y12, x12, x):
    """
    Return linear interpolation between two support points.

    Args:
        :y12: (tuple) y1 and y2 value
        :x12: (tuple) x1 and x2 value
        :x: (float) position for which to return the interpolation

    Returns:
        :y_x: (float) linearly interpolated y(x)
    """

    return y12[0] + (y12[1] - y12[0])/(x12[1] - x12[0])*(x - x12[0])