(11,25-3 целых 5\12+4,3 - 7 целых 19\30):(7 целых 7\12- 5 целых

(11,25 - 3 5/12 + 4,3 - 7 19/30) : (7 7/12 - 5 5/6) = 2 4/7.

1) 11,25 - 3 5/12 = 11 25/100 - 3 5/12 = 11 - 3 + 25/(25 * 4) - 5/12 = 8 + 1/4 - 5/12 = 8 + 3/12 - 5/12 = 8 - 2/12 = 8 - 1/6 = 7 5/6;

2) 7 5/6 + 4,3 = 7 + 4 + 5/6 + 3/10 = 11 + 25/30 + 9/30 = 11 + 34/30 = 11 + 1 4/30 = 12 + 2/15 = 12 2/15;

3) 12 2/15 - 7 19/30 = 12 - 7 + 4/30 - 19/30 = 5 - 15/30 = 5 - 1/2 = 4 1/2;

4) 7 7/12 - 5 5/6 = 7 - 5 + 7/12 - 5/6 = 2 + 7/12 - 10/12 = 2 - 3/12 = 2 - 1/4 = 1 3/4;

5) 4 1/2 : 1 3/4 = 9/2 : 7/4 = 9/2 * 4/7 = (9 * 2 * 2)/(2 * 7) = 18/7 = 2 4/7.