3.
2/3 · 3/2 = 1
1/7 · 7 = 1
4 · 1/4 = 1
1/9 · 9 = 1
18 · 1/18 = 1
4.
poziomo
1 i 4/9 · 9/13 = 1, bo 13/9 · 9/13 = 1
2 i 8/9 · 9/26 = 1, bo 26/9 · 9/26 = 1
8/15 · 1 i 7/8 = 1, bo 8/15 · 15/8 = 1
8/35 · 4 i 3/8 = 1, bo 8/35 · 35/8 = 1
