3 8/9-y=2 7/9, (x-3 12/17)-8 9/17 =4 10/17

3ц8/9-у=2ц7/9у= 3ц8/9-2ц7/9= (3-2)+(8/9-7/9)= 1+1/9= 1ц1/9 (х-3ц12/17)-8ц9/17=4ц10/17х= 4ц10/17+3ц12/17+8ц9/17= (4+3+8)+(10/17+12/17+9/17)= 15+31/17= 15+1ц14/17= 16ц14/17