(1/5 - 5/6) : (1 2/3 +2/5)= - 19/62 (1/2)
1) 1/5 - 5/6=6/30 - 25/30= - 19/30
2) 1 2/3+2/5=1 10/15+6/15=1 16/15=2 1/15
3) - 19/30 : 2 1/15= - 19/30 : 31/15= - 19/30 * 15/31= - 19/62
но если там (1/5+5/6) то
1) 1/5+5/6=6/30+25/30=31/30
2)
3) 31/30 : 2 1/15=31/30 : 31/15=31/30*15/31=15/30=1/2