Separate system solving from single equations in _solve()
Separate system solving from single equations in _solve()

Since the two code paths have no part in common, they should be in
separate functions. This removes a fair bit of unnecessary indentation.

"Flat is better than nested"

vipulroxx/sympy,ga7g08/sympy,kaichogami/sympy,kmacinnis/sympy,souravsingh/sympy,AunShiLord/sympy,Sumith1896/sympy,drufat/sympy,postvakje/sympy,ChristinaZografou/sympy,farhaanbukhsh/sympy,jerli/sympy,skirpichev/omg,madan96/sympy,Davidjohnwilson/sympy,Vishluck/sympy,Shaswat27/sympy,garvitr/sympy,iamutkarshtiwari/sympy,ahhda/sympy,emon10005/sympy,wyom/sympy,shikil/sympy,pbrady/sympy,yukoba/sympy,VaibhavAgarwalVA/sympy,madan96/sympy,oliverlee/sympy,shikil/sympy,srjoglekar246/sympy,garvitr/sympy,atsao72/sympy,MechCoder/sympy,beni55/sympy,skidzo/sympy,Gadal/sympy,moble/sympy,meghana1995/sympy,atsao72/sympy,kevalds51/sympy,AkademieOlympia/sympy,Arafatk/sympy,Gadal/sympy,toolforger/sympy,jbbskinny/sympy,atreyv/sympy,postvakje/sympy,sahilshekhawat/sympy,VaibhavAgarwalVA/sympy,aktech/sympy,skidzo/sympy,asm666/sympy,Shaswat27/sympy,yashsharan/sympy,shikil/sympy,cswiercz/sympy,hrashk/sympy,toolforger/sympy,hrashk/sympy,VaibhavAgarwalVA/sympy,jamesblunt/sympy,hargup/sympy,cccfran/sympy,garvitr/sympy,flacjacket/sympy,lindsayad/sympy,Shaswat27/sympy,sahmed95/sympy,liangjiaxing/sympy,chaffra/sympy,bukzor/sympy,beni55/sympy,MridulS/sympy,diofant/diofant,Curious72/sympy,kaushik94/sympy,souravsingh/sympy,cccfran/sympy,MridulS/sympy,oliverlee/sympy,wanglongqi/sympy,saurabhjn76/sympy,shipci/sympy,rahuldan/sympy,wyom/sympy,postvakje/sympy,Titan-C/sympy,AkademieOlympia/sympy,drufat/sympy,abhiii5459/sympy,farhaanbukhsh/sympy,Mitchkoens/sympy,dqnykamp/sympy,maniteja123/sympy,jaimahajan1997/sympy,vipulroxx/sympy,lidavidm/sympy,Mitchkoens/sympy,Curious72/sympy,jaimahajan1997/sympy,sahmed95/sympy,Designist/sympy,jamesblunt/sympy,ChristinaZografou/sympy,sunny94/temp,moble/sympy,sunny94/temp,saurabhjn76/sympy,bukzor/sympy,yashsharan/sympy,Arafatk/sympy,iamutkarshtiwari/sympy,toolforger/sympy,Davidjohnwilson/sympy,Davidjohnwilson/sympy,pandeyadarsh/sympy,vipulroxx/sympy,abloomston/sympy,amitjamadagni/sympy,sahilshekhawat/sympy,kevalds51/sympy,chaffra/sympy,chaffra/sympy,kmacinnis/sympy,sampadsaha5/sympy,Curious72/sympy,cccfran/sympy,rahuldan/sympy,hargup/sympy,emon10005/sympy,ahhda/sympy,Designist/sympy,kumarkrishna/sympy,yukoba/sympy,iamutkarshtiwari/sympy,mafiya69/sympy,MechCoder/sympy,emon10005/sympy,pandeyadarsh/sympy,Sumith1896/sympy,aktech/sympy,kaichogami/sympy,souravsingh/sympy,Titan-C/sympy,Gadal/sympy,wanglongqi/sympy,cswiercz/sympy,mafiya69/sympy,AunShiLord/sympy,Vishluck/sympy,atreyv/sympy,pbrady/sympy,shipci/sympy,kaushik94/sympy,jbbskinny/sympy,maniteja123/sympy,farhaanbukhsh/sympy,kumarkrishna/sympy,meghana1995/sympy,sahilshekhawat/sympy,dqnykamp/sympy,abloomston/sympy,skidzo/sympy,AunShiLord/sympy,jbbskinny/sympy,debugger22/sympy,cswiercz/sympy,kmacinnis/sympy,jamesblunt/sympy,wanglongqi/sympy,ga7g08/sympy,kumarkrishna/sympy,yukoba/sympy,abhiii5459/sympy,Arafatk/sympy,sampadsaha5/sympy,yashsharan/sympy,amitjamadagni/sympy,rahuldan/sympy,dqnykamp/sympy,aktech/sympy,oliverlee/sympy,moble/sympy,atsao72/sympy,ahhda/sympy,abloomston/sympy,shipci/sympy,grevutiu-gabriel/sympy,hargup/sympy,mcdaniel67/sympy,debugger22/sympy,jaimahajan1997/sympy,Sumith1896/sympy,lindsayad/sympy,sahmed95/sympy,lidavidm/sympy,sampadsaha5/sympy,mcdaniel67/sympy,liangjiaxing/sympy,Titan-C/sympy,liangjiaxing/sympy,asm666/sympy,ChristinaZografou/sympy,debugger22/sympy,jerli/sympy,abhiii5459/sympy,Mitchkoens/sympy,hrashk/sympy,ga7g08/sympy,kaichogami/sympy,kevalds51/sympy,pbrady/sympy,beni55/sympy,lindsayad/sympy,sunny94/temp,bukzor/sympy,mcdaniel67/sympy,AkademieOlympia/sympy,wyom/sympy,asm666/sympy,grevutiu-gabriel/sympy,pandeyadarsh/sympy,meghana1995/sympy,lidavidm/sympy,kaushik94/sympy,MechCoder/sympy,saurabhjn76/sympy,Designist/sympy,maniteja123/sympy,MridulS/sympy,atreyv/sympy,mafiya69/sympy,Vishluck/sympy,drufat/sympy,jerli/sympy,grevutiu-gabriel/sympy,madan96/sympy