Выполните действия а) (1/2+1/5) : 2 - 3/10 б) (3/4 - 5/12) * 8 + 1/18 в) (7/15 + 4/5) : 3 - 1/9 г) (3/7-1/21) * 14 - 1/6

Выполним действия:

а) (1/2 + 1/5) : 2 - 3/10 = 1/20;

1) 1/2 + 1/5 = (1 * 5) / (2 * 5) + (1 * 2) / (5 * 2) = 5/10 + 2/10 = (5 + 2) / 10 = 7/10;

2) 7/10 : 2 = 7/10 * 1/2 = 7/20;

3) 7/20 - 3/10 = 7/20 - 6/20 = 1/20.

б) (3/4 - 5/12) * 8 + 1/18 = 2 13/18;

1) 3/4 - 5/12 = 9/12 - 5/12 = 4/12 = 1/3;

2) 1/3 * 8 = 8/3 = 2 2/3;

3) 8/3 + 1/18 = 48/18 + 1/18 = 49/18 = 2 13/18.

в) (7/15 + 4/5) : 3 - 1/9 = 14/45;

1) 7/15 + 4/5 = 7/15 + 12/15 = 19/15 = 1 4/15;

2) 19/15 : 3 = 19/45;

3) 19/45 - 1/9 = 19/45 - 5/45 = 14/45.

г) (3/7 - 1/21) * 14 - 1/6 = 5 1/6;

1) 3/7 - 1/21 = 9/21 - 1/21 = 8/21;

2) 8/21 * 14 = (8 * 2 * 7) / (3 * 7) = 16/3 = 5 1/3;

3) 16/3 - 1/6 = 32/6 - 1/6 = 31/6 = 5 1/6.