1. 42×7:3=98
2. 12/21у+5/21у-14/21у=3/21у=1/7у
3.(7 1/3 + 2 1/4) : 1/4 - 30 5/6 = 7 1/2
1) 7 1/3 + 2 1/4 = 7 4/12 + 2 3/12 = 9 7/12
2) 9 7/12 : 1/4 = 115/12 * 4 = 115/3 = 38 1/3
3) 38 1/3 - 30 5/6 = 38 2/6 - 30 5/6 = 37 8/6 - 30 5/6 = 7 3/6 = 7 1/2
4. 19.5-0.6=18.9
18.9-2/3=6.3-2=4.3