1) 50+180=180+20+30=230
2) 46-27=46-20-6-1=19
3) 56:4=14
4) 40*5=4*5*10=200
Насколько поняла условие- в 3-й день продано: 800-320-320*0.6=288
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1. 2х/36 = 5/6 2. 4/9 = 3х/54
2х = 36*5/6 3х = 4*54/9
2х = 30 3х = 24
х = 15 х = 8