1)1/2-1/7=7/14-2/14=5/14
2)5/14-1/4=10/28-7/28=3/28
3)2 5/14 - 1 8\21=33\14-29/21=198/84-116/84=82/84=41/42
4)41/42-1/3=41/42-14/42=27/42
5)3/28 : 27/42 = 3*42 / 28*27 = 126/756=1/6
6)5.3*0.7=3.71
7)3.71=1.29=5
8)1.04:0.8=1.3
9)7.3-1.3=6
10)5:6=5/6
11)1/6+5//6=1