вычеслите 3/7+4/9 8.9-7.8 13/15-2/3 20/21+3/7 17/18-11.12 7.16 +1.6 2/9+5/6 10/21+9/14 7/9-4/15

3/7+4/9=27/53+28/53=55/53=1 2/538,9-7,8=1,113/15-2/3=13/15-10/15=3/15=1/520/21+3/7=20/21+9/21=29/21=1 8/2117/18-11/12=34/36-33/36=2/36=1/187,16+1,6=8,962/9+5/6=4/18+15/18=19/18=1 1/1810/21+9/14=140/294+189/294=329/294=47/42=1 5/427/9-4/15=105/135-36/135=69/135=23/45