30-28,1:(5 7/20-4 6/35)

1)5 7/20-4 6/35=107/20-146/35=7*107/140-4*146/140=749/140-584/140=165/140=1 25/140=1 5/28
2)28,1:1 5/28=281/10:33/28=281/10*28/33=281/5*14/33=3934/165=23 139/165
3)30-23 139/165=30/1-3934/165=30*165/165-3934/165=4950/165-3934/165=1016/165=6 26/165