А) 2 4/5 : (7 2/3 - 5 4/5) = 1 1/2
1) 7 2/3 - 5 4/5 = 7 10/15 - 5 12/15 = 6 25/15 - 5 12/15 = 1 13/15
2) 2 4/5 : 1 13/15 = 14/5 : 28/15 = 14/5 * 15/28 = (1*3)/(1*2) = 3/2 = 1 1/2
б) 20 - ((5 3/4 - 2 1/2) : 1/4 + 5 9/11) = 1 2/11
1) 5 3/4 - 2 1/2 = 5 3/4 - 2 2/4 = 3 1/4
2) 3 1/4 : 1/4 = 13/4 * 4/1 = 13
3) 13 + 5 9/11 = 18 9/11
4) 20 - 18 9/11 = 19 11/11 - 18 9/11 = 1 2/11