13/15z-(7/9+1/3z)=7 9/2
13/15z-(7/9+1/3z)=7 2/9 13/15z-7/9-1/3z=7 2/9 13/15z-1/3z=7 2/9+7/9 13/15z-5/15z=11 5/18 +14/18 8/15z=12 1/18 z=12 1/18:8/15 z=22 29/48