Capacitor Diagram Transormations

[dwn]

I am having a difficult time understanding how they're transforming this capacitor schematic...what exactly is going on here? The example states that each cap is 7pF and the final answer C(eq) = 4.308pF...but why?

 

[NascentOxygen]

There should be 3 figures to illustrate what the dialogue is describing, The first figure would be identical to that in your image #2. Then the Y network at its centre is transformed to Δ, producing the figure you have as image #1.

Finally, to consolidate the topic, they set you an exercise to apply what you have learnt, and this exercise is centred around your image #2.

You'll need the formulae for these impedance transformations, presumably your lectures have covered the topic? http://www.allaboutcircuits.com/vol_1/chpt_10/13.html