X-9=7♦♦♦♦♦♦♦ x+30=70
x= 7+9 или 9+7♦ x=70-30
x=16♦♦♦♦♦♦♦♦ x=40
16-9=7♦♦♦♦♦♦ 40+30=70
7=7 ♦♦♦♦♦♦♦♦♦70=70
400с=6 минут, 40секунд;;
250с=4минути 10 секунд;
1600с=26минут40секунд;
15 целых 12/18 + 12 3/9 = 15 12/18 + 12 6/18 = 27 18/18 = 28
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15 целых 12/18 + 12 3/9= 15 2/3 + 12 1/3 = 27 3/3 = 28