(10 4/3-х)-5 11/13=3 7/13

Преобразуем смешанные дроби в обыкновенные:

1) 10 4/3 = (10 * 3 + 4)/3 = (30 + 4)/3 = 34/3;

2) 5 11/13 = (5 * 13 + 11)/13 = (65 + 11)/13 = 76/13;

3) 3 7/13 = (3 * 13 + 7)/13 = (39 + 7)/13 = 46/13;

34/3 - х - 76/13 = 46/13;

х = 34/3 - 76/13 - 46/13 = 34/3 - 122/13 = 13 * 34/39 - 3 * 122/39 = 442/39 - 366/39 = 76/39;

Ответ: х = 76/39.