Why did shakespeare include the three weird sisters in macbeth?

Can someone me with my essay? editing?

Atheme from letter 4 in frankenstein is “friendship is sometimes born in the most unconventional places and situations.” this theme is conveyed through the conversations between walton and frankenstein, and these talks lead them to become confidants and friends. describe a theme from letter 3 of frankenstein and a different theme from letter 4. how are these themes conveyed in each letter? provide evidence from the text to support the themes expressed in each letter.

One way to show a character is a) to use dialogue b) use dynamic sentences c) interview friends d) share details