в) 5/9 ÷ (1/2 - 1/3);

в) 5/9 ÷ (1/2 - 1/3) = 5/9 ÷ (3/6 - 2/6) = 5/9 ÷ (1/6) = 5/9 * 6/1 = 30/9 = 10/3 = 3 1/3