5/14 = 15/42
8/21 = 16/42
15/42 < 16/42
5/14 < 8/21
12×3.14=37.68см. Длина окружности
5х+у=14 (домножить всё уравнение на 3)
2х-3у=9
15х=3у=42
2х-3у=9
17х=51
2х-3у=9
х=3
6-3у=9
х=3
-3у=3
х=3
у=-1
1)637 637:7=91 091
2)91 091:11=8 281
3)8 281:13=637
4)637*1001=1 638
ответ1 638
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