79/80 - (3/16+39/80),2/45 + (41/45-7/9),7/15 (2/15+1/5),3/16 + (15/16-5/8)

79/80 - (3/16+39/80) = 5/16

3/16+39/80 = (3*5+39) / 80=54/80

79/80-54/80 = (79-54) / 80=25/80=5/16

2/45 + (41/45-7/9) = 8/45

41/45-7/9 = (41-7*5) / 45=6/45

2/45+6/45 = (2+6) / 45=8/45

7/15 - (2/15+1/5) = 2/15 (здесь знак пропущен?! я поставила -)

2/15+1/5 = (2+1*3) / 15=5/15

7/15-5/15 = (7-5) / 15=2/15

3/16 + (15/16-5/8) =

15/16-5/8 = (15-2*5) / 16=5/16

3/16+5/16 = (3+5) / 16=8/16=1/2