Выполните действие 2/9+1/9. 3/5+2/7. 11/15-3/5. 5/6-1/4

Вычислим значения выражений:

1) 2/9 + 1/9 = (2 * 1 + 1 * 1)/9 = (2 + 1)/9 = 3/9 = 3/(3 * 3) = 1/(1 * 3) = 1/3; 

2) 3/5 + 2/7 = (3 * 7 + 2 * 5)/35 = (21 + 10)/35 =  31/35; 

3) 11/15 - 3/5 = (11 * 1 - 3 * 3)/15 = (11 - 9)/15 = 2/15; 

4) 5/6 - 1/4 = (5 * 2 - 1 * 3)/12 =(10 - 3)/12 = 7/12.