A) 6.56-(5.56-7.5)-(4.2-7.89)=6.56-5.56+7.5-4.2+7.89=12.19
Б) -(5,23-2,5)-(-4,23+10)=-5,23+2,5-4,23-10=-6,5
В) -(7 и 4/7 - 10 и 1/3) - 8 и 4/7 + 3 и 1/3 = -(7 и 4/7)+ 10 и 1/3 - 8 и 4/7 + 3 и 1/3=13 и 2/3 - 16 и 1/7 = -(2 и 10/21)
Г) 2 и 4/15 - (-10,4+4 и 7/15)= 2 и 4/15 + 10,4 - 4 и 7/15 = -2 и 1/5 + 10,4 = -2,2+10,4 = 8,2