С.номера 442 и 444. 442: 1/12 + 3/4; 1/2 + 3/8; 17/1000 + 81/100. 444: 11/16 - 3/8; 5/6 - 5/12; 4/7 -8/21; 17/30 -4/15.

1/12+3/4=1/12+9/12=10/12
1/2+3/8=4/8+3/8=7/8
17/1000+81/100=17/1000+810/1000=827/1000

11/16-3/8=11/16-6/16=5/11
5/6-5/12=10/12-5/12=5/12
4/7-8/21=12/21-8/21=4/21
17/30-4/15=17/30-8/30=9/30