Please help chemistry

What is Ag+ and N3- as a formula together?

How do scientists think that gravity affected the formation of our solar system?

Explanation for basic character?

Indicate whether the specified alkyl halides will form primarily substitution products, only elimination products, both substitution and elimination products, or no products when they react with sodium methoxide. 1-bromobutane 1-bromo-2-methylpropane 2-bromobutane 2-bromo-2-methylpropane