Add commas ... please check and correct me.

Add commas to divide the separate parts of the following sentences.

Sally bought some flowers for her house but they wilted in the heat.
Sally bought some flowers for her house, but they wilted in the heat.

Billy had always wanted to be a writer although he didn’t know where to start.
Billy had always wanted to be a writer, although he didn’t know where to start.

The boys were excited to go to the theme park but he was too small for the rides.
The boys were excited to go to the theme park, but he was too small for the rides.

Dan’s room was tidy and that was how his mother liked it.
Dan’s room was tidy, and that was how his mother liked it.

Amanda’s homework was submitted a day early which was very unusual for her.
Amanda’s homework was submitted a day early, which was very unusual for her.