Дроби к общему знаменателю: 2/15 и 5/12, 5/12 и 7/8, 6/15 и 11/18, 5/16 и 5/12 , 7/33 и 3 /77, 2/55 и 5/22 , 4/15 и 3/20, 5/121 и 8/99, 1/72 и 1/56, 1/48 и 1/72, 2/77 и 3/44, 1/51 и 1/68

1) 8/60 и 25/60

2) 10/24 и 21/24

3) 36/90 и 55/90

4) 15/48 и 20/48

5) 49/231 9/231

6) 4/110 и 25/110

7) 16/60 и 9/60

8) 45/1089 и 88/1089

9) 7/504 и 9/504

10) 9/432 и 6/432

11) 8/308 и 21/308

12) 4/204 3/204