Question

Решите примеры,только подробно:

1/2+1/3=
1/4+2/5=
2/3+1/4=
3/4+2/4=
5/7-1/6=
3/4-1/3=
1/8+1/4=
2/3-5/9=
1/2-5/12=
5/12-2/9=
1/8+7/12=
3/4-1/6=
5/9+3/4=
23/40-3/8=
9/35-9/28=