9 - 2 1/2 : 3 3/4 - (2 1/2 - 1/3) * 12 = - 17 целых 2/3
1) 2 1/2 - 1/3 = 2 3/6 - 2/6 = 2 1/6 = 13/6
2) 13/6 * 12 = 13 * 2 = 26
3) 2 1/2 : 3 3/4 = 5/2 : 15/4 = 5/2 * 4/15 = (1*2)/(1*3) = 2/3
4) 9 - 2/3 = 8 3/3 - 2/3 = 8 1/3
5) 8 1/3 - 26 = - (26 - 8 1/3) = - (25 3/3 - 8 1/3) = - 17 2/3