If it sill doesn't solve your problem then please consider uploading a sample file and give a manual layout of the input and output data of what you are envisioning..
If it needs to be 43179 you either need to adjust A2's value or your tax rate. Your problem is still not clear. Can you state clearly what you are after??
I am sorry but your problem is still not clear to me.
It looks like your expected result(43179.125) is 11.11% of Total Value = 388612.13. And you are trying to find out 12.5% Tax Value from the Total Value (388612.13) which is to me nothing but =A2*12.5/100. But this will not give you the result (43179.125) you are expecting.
Can you explain what is the logic of this formula?