Question

Помогите решить пожалуйста )
1 ) (1/2 - 1/5 ) - ( 4/15 - 7 / 30 ) - 2/15 = ?
2) (3/5 - 1/7 ) - (13/15 - 1/2 ) - 1/21 = ?
3) (25/28 - 5/14 ) - ( 5 /7 - 1/4 ) - 1/28 = ?
4) (35/36 - 5/8 ) - ( 17 /18 - 7/ 9 ) - 5 / 72 = ?

Answer 1

1) (1/2-1/5)-(4/15-7/30)-2/15=(5/10-2/10)-(8/30-7/30)-2/15=
=3/10-1/30-2/15=9/30-1/30-4/30=4/30=2/15

2)(3/5-1/7)-(13/15-1/2)-1/21=(21/35-5/35)-(26/30-15/30)-1/21=
=16/35-11/30-1/21=96/210-77/210-10/210=9/210=3/70

3)(25/28-5/14)-(5/7-1/4)-1/28=(25/28-10/28)-(20/28-7/28)-1/28=
=15/28-13/28-1/28=1/28

4)(35/36-5/8)-(17/18-7/9)-5/72=(70/72-45/72)-(17/18-14/18)-5/72=
=25/72-3/18-5/72=25/72-12/72-5/72=8/72=1/9