а)(40*x):10=28 б)y:9-28=32 в)39+490:k=46 г)(25-a)*7=63

а) (40 x) 10 = 28;

40x 10 = 28;

40x = 28 10;

40x = 280;

x = 280 40;

x = 7;

Проверим:

(40 7) 10 = 28;

280 10 = 28;

28 = 28;

б) y 9 - 28 = 32;

y 9 = 32 + 28;

y 9 = 60;

y = 60 9;

y = 540;

Проверим:

540 9 - 28 = 32;

60 - 28 = 32;

32 = 32;

в) 39 + 490 k = 46;

490 k = 46 - 39;

490 k = 7;

k = 490 7;

k = 70;

Проверим:

39 + 490 70 = 46;

39 + 7 = 46;

46 = 46;

г) (25 - a) 7 = 63;

(25 - a) = 63 7;

25 - a = 9;

-a = - 25 + 9;

-a = -16;

a = 16;

Проверим:

(25 - 16) 7 = 63;

9 7 = 63;

63 = 63;

Все правильно.