Can you check these? Place commas where they belong.

4. No Elena isn't coming over this weekend so you can make plans to hang out with your friends.

A: No, Elena isn't coming over this weekend, so you can make plans to hang out with your friends.

13. Carly was craving chocolate ice cream so she changed out of her pajamas and headed to the store.

A: Carly was craving chocolate ice cream, so she changed out of her pajamas and headed to the store.

16. After we spend all this time researching we will definitely understand and know all about Westward Expansion.

A: After we spend all this time researching, we will definitely understand and know all about Westward Expansion.

All 3 of your corrected sentences are fine.

Thanks!

You're welcome.

To check for the correct placement of commas, you can follow these general guidelines:

1. Use commas to separate independent clauses in a compound sentence. This means that if two independent clauses are joined by a coordinating conjunction (such as "and," "but," "or," "so," etc.), a comma is needed before the conjunction.

2. Use a comma after an introductory phrase or clause. If a sentence begins with a phrase or clause that sets the context or provides additional information, it is usually followed by a comma.

Now, let's check the placement of commas in the provided sentences:

4. No Elena isn't coming over this weekend so you can make plans to hang out with your friends.
- In this sentence, "No" seems to be an introductory word or phrase expressing a strong emotion. Therefore, it requires a comma after it.
Corrected: No, Elena isn't coming over this weekend, so you can make plans to hang out with your friends.

13. Carly was craving chocolate ice cream so she changed out of her pajamas and headed to the store.
- This sentence consists of two independent clauses connected by the coordinating conjunction "so." Therefore, it needs a comma before "so."
Corrected: Carly was craving chocolate ice cream, so she changed out of her pajamas and headed to the store.

16. After we spend all this time researching we will definitely understand and know all about Westward Expansion.
- "After we spend all this time researching" is an introductory clause that adds context. Hence, it requires a comma after it.
Corrected: After we spend all this time researching, we will definitely understand and know all about Westward Expansion.

By following these guidelines and checking for introductory phrases, coordinating conjunctions, and independent clauses, you can determine the correct placement of commas.