2)11 7/12+6 11/18=11 21/36+6 22/36=17 43/36=18 7/36
3)7 8/15+8 17/20=7 32/60 + 8 51/60=15 83/60=16 23/60
4)7 3/8+9 7/16+11 7/12=7 18/48+9 21/48+11 28/48=27 67/48=28 19/48