выполни действия: 3/8+7/16 б) 11/12-7/15 в) 11/15-3/20+1/30 реши уровнение: б-13/15=13/45

1) 3/8 + 7/16 = 3/8 * 2/2 + 7/16 = 6/16 + 7/16 = 13/16;

2) 11/12 - 7/15 = 11/12 * 15 - 7/15 * 12/12 = 165/180 - 84/180 = 81/180 = 81/180 : 9/9 = 9/20;

3) 11/15 - 3/20 + 1/30 = 12/15 * 4/4 - 3/20 * 3/3 + 1/30 * 2/2 = 48/60 - 9/60 + 2/60 = 39/60 - 2/60 = 37/60;

б - 13/15 = 13/45;

б = 13/45 + 13/15;

б = 13/45 + 13/15 * 3/3;

б = 13/45 + 39/45;

б = 52/45 = 52 : 45 = 1,16.

Проверим.

52/45 - 13/15 = 13/45;

52/45 - 13/15 * 3/3 = 13/45;

52/45 - 39/45 = 13/45;

13/45 = 13/45.