Let "b" represent the number of biscuits Jacky baked.
.. container A holds (3/7)b
.. container B holds (1 -3/7)*(5/8)b = (5/14)b
.. container C holds (1 -3/7 -5/14)b = (3/14)b = 168
Then
.. b = 168/(3/14) = 784
Jacky baked 784 biscuits.
AB^2 + BC^2 = AC^2
AB^2 + 6^2 = square root 117^2
AB^2 + 36 = 117
Now subtract 117 from both sides
AB^2 = 81
AB = square root 81 = 9

Therefore AB is 9 cms.