1) 6 (7/12) - 3 (17/36) = 79/12 - 125/36 = 79/12 (и числитель, и знаменатель *3) - 125/36 = 237/36 - 125/36 = 112/36 = 28/9.
2) 28/9 * 2,5 = 28/9 * 5/2 = (28*5)/(9*2) = 140/18 = 70/9.
3) 4 (1/3) : 0,65 = 13/3 : 65/100 = 13/3 : 13/20 = 13/3 * 20/13 = 20/3.
4) 70/9 - 20/3 = 70/9 - 60/9 = 10/9 = 1 (1/9).
Ответ: 1 (1/9).