1) 3/8 : 3 = 3/8 · 1/3 = 1/8
2) 5/8 + 1/8 = 6/8 = 3/4
3) 4/9 : 3/4 = 4/9 · 4/3 = 16/27
4) 1 5/9 - 16/27 = 1 15/27 - 16/27 = 42/27 - 16/27 = 26/27
5) 0,9 · 26/27 = 9/10 · 26/27 = (1·13)/(5·3) = 13/15