Va rog, ajutați-mă la aceste doua punte!

Răspuns:
b) 3•4/17:55/51
12/17•51/55
12•51/17•55
12•3/55
36/55
c) 1/7:3/5 / 3/7•5/6
1/7•5/3 / 3/7•5/6
5/21•42/15
1•2/3
2/3