446
1)1/3+4/5-1/12= (20+48-5) / 60 = 63/60 = 21/20 = 1,05
2) 2/7-1/6+1/9= (36-21+14) / 126=29/126
447
1) х = 2/3+2/7-4/21
х = (14+6-4) / 21
х = 16/21
2) у = 4/5-3/10-1/4
у = (16-6-5) / 20
у = 5/20 = 1/4 = 0,25
3) -х = 7/10-4/5-13/20
-х = (14-16-13) / 20
-х = -3/4
х = 3/4 = 0,75
4) -х = 1/3-2/3+2/9
-х = (3-6+2) / 9
-х = -1/9
х = 1/9