Так это легко. 120 :3=40.и всё
3/18+2/3=3/18+12/18=15/18=5/6
6/15+7/20=24/60+21/60=45/60=3/4
1/12+3/4=1/12 +9/12=10/12=5/6
6/14+7/21=18/42+14/42=32/42=16/21
2/45+5/9=2/45+25/45=27/45=3/5
4/21+6/28=16/84+18/84=34/84=17/42
1/42+2/14=1/42+6/42=7/42=1/6
<span>8/18+6/27=4/9+2/9=6/9=2/3</span>
34.2-17.9+у=22
у=22+17.9-34 .2
у=39.9-34.2
у=5.7