me translate stuff yu tipe tu be:
(640/9)=(-10/3)*((23/6b)+(5/3))
or (640/9)*((23/6b)+(5/3))=-(10/3)
so ((23/6b)+(5/3))=-(10/3)-(640/9)
so (23/6b)=-(10/3)-(640/9)-(5/3)=-(15/3)-(640/9)=-(45+640)/9=-685/9
23/6=-(685/9)b
so b=-(23/6)*(9/685)=-207/4110=-69/1370=-0.05036496