No Algebra needed.

(sfrose's explanation is better than anything I could have written , so I thought instead I would mention how to recognize innermost crossbreeds.)

since the program keeps track of all your seeds, you actually don't have to break this down. what you do is find the innermost crossbreeds and do them, place their seeds in your seed tray so VST knows about them, and then go look at the chart again. You will know an innermost crossbreed because it looks like this:

[plant1] x [plant2]

Notice it has ] x [ in the middle. Not ] x [[ , not ]] x [[ , and not ]] x [ .

Back to our example:

[[[[fragrant ball cactus] x [[citrus maranta] x [[citrus maranta] x [fourpetal maple]]]] x [citrus maranta]] x [fragrant ball cactus]] x [[[[fragrant ball cactus] x [[citrus maranta] x [[citrus maranta] x [fourpetal maple]]]] x [citrus maranta]] x [[[[fragrant ball cactus] x [[citrus maranta] x [[citrus maranta] x [fourpetal maple]]]] x [citrus maranta]] x [citrus maranta]]]

The [citrus maranta] x fourpetal maple] is an innermost crossbreed 3 times up there. once you do that crossbreed and place whatever seed results from that in your seed tray, and go back to the chart, you will find that VST will replace that crossbreed with the name of the seed that resulted, giving you new innermost crossbreeds to do. after just a few cycles of doing the innermost crossbreeds, you will have the plant you want.

Cheers,
-Borg