Приведите дроби к общему знаменателю и выполните действия 1/4 +5/6;3/20+ 7/25;2/9+1/6;5/6-3/8;9/10-3/4;3/10-2/15;

1) 1/4 + 5/6 = 3/12 + 2 * 5/12 = (3 + 10)/12 = 13/12;

2) 3/20 + 7/25 = 5 * 3/100 + 4 * 7/100 = (15 + 28)/100 = 43/100;

3) 2/9 + 1/6 = 2 * 2/18 + 3/18 = (4 + 3)/18 = 7/18;

4) 5/6 - 3/8 = 4 * 5/24 - 3 * 3/24 = (20 - 9)/24 = 11/24;

5) 9/10 - 3/4 = 2 * 9/20 - 5 * 3/20 = (18 - 15)/20 = 3/20;

6) 3/10 - 2/15 = 3 * 3/30 - 2 * 2/30 = 5/30 = 1/6.