Songs won't download onto iPhone?

At first I thought it was because they were not in mp3 format, but I double checked and they definitely are and I have the newest version of iTunes. Please help! I have no idea what to do, 50 songs are just not showing up.

Added (1). Oh, and I have enough space to add the songs, so that's not the problem.

Added (2). And they're all checked to include them…

When you connect your iPhone and it shows up on the side panel click it. You'll see tabs at the top. Click on the music tab. Make sure the option to "sync music" is checked. If its not, check it and click apply.

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