Найдите значение выражения (1/4+1/5)-(3/35-1/28)

1) 12 : 3 3/8 - 1 1/4 : 15/32=12/1 * 8/27 - 5/4 * 32/15=4/1 * 8/9 - 1/1 * 8/3=
32/9 - 8/3=(32-24)/9=8/9;
2) 1 31/35 : (2 - 8/9 : 1 19/45)=66/35 : (2 - 8/9 * 45/64)=66/35 : (2 - 1/1 * 5/8)=
66/35 : (2 - 5/8)=66/35 : 11/8=66/35 * 8/11=6/35 * 8/1=48/35=1 13/35;
3) (1 1/35 : 4/5 - 1 8/35) * 3 1/3=(36/35 * 5/4 - 43/35) * 10/3=(9/7 * 1/1 - 43/35) * 10/3=
(9/7 - 43/35) * 10/3=(45-43)/35 *10/3=2/35 * 10/3=2/7 * 2/3=4/21;
4) (7 - 1 5/9 : 7/24) : 20/27=(7 - 14/9 * 24/7) * 27/20=(7 - 2/3 * 8/1) * 27/20=
(7 - 16/3) * 27/20=(7-5 1/3) * 27/20=1 2/3 * 27/20=5/3 * 27/20=1/1 * 9/4=9/4=2 1/4. я старался!:)