А) 15/19-7/19+4/19=12/19
б) 7ц.5/14+3ц.11/14=10ц.16/14=11ц.2/14=11ц.1/7
в) 5-2ц.4/11=3ц.-4/11=2ц.7/11
г) 8ц.2/9-2ц.4/9=7ц.11/9-2ц.4/9=5ц.7/9
.........
3ц.4/15+у=7ц.1/15
у=7.1/15-3.4/15
у=6.16/15-3.4/15
у=3ц.12/15
у=3ц.4/5
.............
б)
5.4/13-у=4.5/13
у=5.4/13-4.5/13
у=4.17/13-4.5/13
у=17/13-5/13
у=12/13
............