12) 7/5 = 7÷5 = 1,4 = 1
12/5 = 12÷5 = 2,4 = 2
12/3 = 12÷3 = 4
18/7 = 18÷7 = 2,5 = 2
21/5 = 21÷5 = 4,2 = 4

14) 13/5 = 13.2/5.3 = 26.4/10.4 = 104/40
7/14 = 7÷7/14÷7 = 1/2 = 7.2/14.2 = 14/28
5/2 = 5.3/2.3 = 15/6 = 15.2/6.2 = 30/12
45/18 = 45÷9/18÷9 = 5/2 = 5.3/2.3 = 15/6
3/21 = 3÷3/21÷3 = 1/7 = 1.10/7.10 = 10/70