Помогите, 5/6+5/18 - (3 целых7/9-2 целых13/15) = ?

5/6 + 5/18 - (3 7/9 - 2 13/15) = 1/5

1) 3 7/9 - 2 13/15 = 3 35/45 - 2 39/45 = 2 80/45 - 2 39/45 = 41/45

2) 5/6 + 5/18 = 15/18 + 5/18 = 20/18 = 1 2/18 = 1 1/9

3) 1 1/9 - 41/45 = 1 5/45 - 41/45 = 50/45 - 41/45 = 9/45 = 1/5

Пояснения:

7/9 = (7*5) / (9*5) = 35/45 - доп. множ. 5

13/15 = (13*3) / (15*3) = 39/45 - доп. множ. 3

3 35/45 = 2 45/45 + 35/45 = 2 80/45

5/6 = (5*3) / (6*3) = 15/18 - доп. множ. 3

2/18 = (2:2) / (18:2) = 1/9 - сократили на 2

1/9 = (1*5) / (9*5) = 5/45 - доп. множ. 5

1 5/45 = 45/45 + 5/45 = 50/45

9/45 = (9:9) / (45:9) = 1/5 - сократили на 5