<PRE><B>Question 812829</B>
I know I solved this a few days ago but here we go again.
18/a+18/b=1,
24/b+24/c=1,
36/a+36/c=1,
x/a+x/b+x/c=1
a = 48,   b = 144/5,   c = 144,   x = 16
16 days for a b and c

another way
1/a+1/b    =1/18,
    1/b+1/c=1/24,
1/a+    1/c=1/36,
2/a+2/b+2/c=1/8

1/a+1/b+1/c=1/x
x=16
</PRE>