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Both challenges requires only a bit of good will and creativity.

As you can see above memechallenge is working on this way : In posts like this i put picture and your job is to make best possible meme of it..
So you make meme and you post it with first tag #memechallenge ... And you are in!

On other way #steemitphotochallenge works like this: @jamtaylor publish weekly theme and your job is to post maximum 3 entries with tags #steemitphotochallenge (first) and #photography.

Thank you for your comment and hope to see your entries on both challenges!

oh but the meme one is open daily? and does it have to be only one submission? and is this meme challenge already over? how do you know if a meme challenge has ended and when to await the next one?

Memechallenge is also weekly but you could find all those information in rules above

Rules:
Title of every entry must contain "Meme challenge # - Entry #"
First tag of post must be #memechallenge
Each user can have up to 3 entries that will be considered in challenge
Your meme must contain text
You can add/remove something from original photo but again photo without text isn't meme

End of challenge will be on Sunday at 12:00 (UTC +1)