3/7 + 1/6 + 5/14 5/12 + 2/9 + 1/18 1/2 + 1/3 + 1/9

1) 40/42
2) 25/36
3) 17/18

1)3/7+1/6+5/14=6/14+5/14+1/6=11/14+1/6=33/42+7/42=40/42=20/21
2)5/12+2/9+1/18=5/12+4/18+1/18=5/12+5/18=15/36+10/36=25/36
3)1/2+1/3+1/9=1/2+3/9+1/9=1/2+4/9=9/18+8/18=17/18