1) (7/15 - 1/6) + 2/5
Common denominator for 15 and 6 is 30:
(14/30 - 5/30) + 12/30
= 9/30 + 12/30
= 21/30
= 7/10
Adding 2/5:
7/10 + 2/5
Common denominator for 10 and 5 is 10:
(7/10 1/1) + (2/5 2/2)
= 7/10 + 4/10
= 11/10
= 1 1/10

2) (3/8 - 1/9) + 25/36
Common denominator for 8 and 9 is 72:
(27/72 - 8/72) + 25/36
= 19/72 + 25/36
Common denominator for 72 and 36 is 72:
(19/72 2/2) + (25/36 2/2)
= 38/72 + 50/72
= 88/72
= 11/9
= 1 2/9