kak tolong jawab soal ya kak, pakai caranya

nomor7.
1/2+7 4/5 -7 9/10=
  1/2 +39/5-79/10=
  5/10 +78/10 -79/10 =4/10=2/5
nomor 8
4 1/2 -2 4/5=
9/2-14/5=
45/10-28/10=17/10
nomor 9
2 3/4 +3 1/2+ 5 7/10=
11/4 +7/2 +57/10=
55/20 +20/20+114/20=239/20
nomor 10
2/5-1/4=
8/20-5/20=3/20