Answer:
b=20/3
Step-by-step explanation:
i assume this is what you want, what b equals. So first set both equations equal to each other and then just algebraically manipulate them.
b-20=-2b Here add 20 to both sides and 2b to both sides
3b=20 Here divide both sides by 3
b=20/3
Let me know if you need any more help.