Question 257965
6/a+6/b+6/c=1
9/b+9/c=1 
8/a+8/c=1
a = 18 days,   b = 24 days ,   c = 72/5 = 14.4 days
check 1
6/18+6/24+30/72=1
24/72+18/72+30/72=1
ok 1

check 2
9/24+45/72=1
27/72+45/72=1
ok2
check3
8/18+40/72=1 
32/72+40/72=1
ok3