4) (3 1/4 + 2 1/6) : 2 3/5 - 2/3 * 4/9;

4) (3 1/4 + 2 1/6) : 2 3/5 - 2/3 * 4/9 = (13/4 + 13/6) : 13/5 - (2 * 4)/(3 * 9) = (13 * 3)/(4 * 3) + (13 * 2)/(6 * 2) : 13/5 - 8/27 = (39/12 + 26/12) : 13/5 - 8/27 = (39 + 26)/12 : 13/5 - 8/27 = 65/12 * 5/13 - 8/27 = (65 * 5)/(12 * 13) - 8/27 = (5 * 5)/(12 * 1) - 8/27 = 25/12 - 8/27 = (25 * 9)/(12 * 9) - (8 * 4)/(27 * 4) = 225/108 - 32/108 = (225 - 32)/108 = 193/108 = 1 85/108

Ответ: 1 85/108