1)х+13,85=30
х=30-13,85
х=16.15
2) с+12.76=40
с=40-12.76
с=27.24
3) 27.31+7.35+у=62.7
34.66+у=62.7
у=62.7-34.66
у=28.04
4) 1.3+n=6.7
n=6.7-1.3
n=5.4
2000 - 5%
X - 100%
X=2000*100/5
X=40000 рублей
800+400=1200см 8м=8*100=800см,40ДМ=40*10=400СМ
(х - 20,9) + 12,27 = 23,2
х - 20,9 = 23,2 - 12,27
х - 20,9 = 10,93
х = 10,93 + 20,9
х = 31,83
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Проверка:
(31,83 - 20,9) + 12,27 = 23,2
10,93 + 12,27 = 23,2
23,2 = 23,2