(2 3/7+1 5/9)-(1 4/7+5/9); -(2,77-7 2/9)-(0,23- 4 7/9); -(5/6+1,37)-(2,87-1/3):

2 3/7 + 1 5/9 - 1 4/7 - 5/9 = 2 3/7 - 1 4/7 + 1 5/9 - 5/9 = 10/7 - 4/7 +1= 1 6/7-2,77+ 7 2/9 - 0,23 + 4 7/9 = -3 + 12=9-5/6 - 1,37 - 2,87 + 1/3 = - 4,24 - 5/6 + 1/3 = -4,24 (-5+2)/6 = - 4,24 - 3/6= - 4,24 -1/2 = -4,24 - 0,5 = - 4,74