1) 5,45 : 6 8/35 = 545/100 : 218/35 = 109/20  * 35/218 = 7/8

2) 2 9/16 + 7/8 = 2 9/16 + 14/16 = 2 23/16 = 3 7/16

3) 3 7/16 : 6 1/9 = 55/16 : 55/9 = 55/16 * 9/55 = 9/16

ответ: 9/16