1) x = 5 3/18 + 2 7/12 = (5+2) + (3/18+7/12) = 7 + 6/36 + 21/36 = 7 27/36 = 7 3/4
2) x = 100 5/28 + 26 7/21 = (100+26) + (5/28+1/3) = 126 + 15/84 + 28/84 = 126 43/84
3) x = 15 16/45 + 37 17/54 = (15+37) + (16/45+17/54) = 52 + 96/270 + 85/270 = 52 181/270
4) x = 42 17/35 + 33 21/25 = (42+33) + (17/35+21/25) = 75 + 85/175 + 147/175 = 75 232/175 = 76 57/175