решите уравнения исделайте проверку:400+f:80=600
500*x-600=400
1300-(b+800)=400
600*20-n=60
(600-500):y=20
d:(1300-800)=4

400+f:80=600                  500*Х-600=400        1300-(b+800)=400
400+f=600*80                  500*Х=400+600       b+800=1300-400
400+f=48000                   500*Х=1000             b+800=900
f=48000-400                    Х=1000:500             b=900-800
f=47600                           Х=2                        b=100
Проверка                        Проверка                Проверка
400+47600:80=600           500*2-600=400        1300-(100+800)=400
1)400+47600=48000         1)500*2=1000          1)100+800=900
2)48000:80=600                2)1000-600=400      2)1300-900=400

600*20-n=60                    (600-500):у=20         d:(1300-800)=4
20-n=60:600                    100:у=20                  d:500=4
20-n=0,1                          у=100:20                 d=4*500
n=20-0,1                          у=5                         d=2000
n=19,9                             Проверка                Проверка
Проверка                         (600-500):5=20        2000:(1300-800)=4
600*20-19,9=60                 1)600-500=100        1)1300-800=500
1)20-19,9=0,1                    2)100:5=20             2)2000:500=4
2)600*0,1=60

1) 500х-600=400
500х=400+600
500х=1000
х=1000:500
х=2
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Проверка:
500*2-600=400