12. Выполните действия. А) (7/8 - 1/8) + 1/4; Б) (5/6 + 7/6) - 1/7; В) (7/3 - 4/3) - 12/13; Г) 4/3 - (9/11 + 2/11).
(7/8 - 1/8)+1/4=6/8+1/4=3/4+1/4=4/4=1 (5/6+7/6) -1/7=12/6 - 1/7=2 -1/7=1 6/7 (7/3 - 4/3) -12/13=3/3 - 12/13=1 - 12/13=1/13 4/3 - (9/11+2/11)=4/3 - 11/11=4/3 - 1=1 1/3 -1=1/3