Last week I was in the middle of teaching 1-step equations to my freshman classes. I drew four large "clouds" on my boards and gave each student 4 sticky notes.
In one cloud I wrote "Write an equation where you would need to add to solve it." the next was subtract, then multiply and finally divide.
I told the students to write one equation on each sticky and place it in the appropriate cloud. Each student should place one sticky in each cloud. They were to only write the equation and not solve it.
Once all students were done, I assigned the students to a cloud. The students then solved all the equations in that particular cloud. If they felt that a sticky should be in a different cloud, they were to hand it to that group. If they felt that an equation didn't belong in any of the clouds (maybe it was a two-step equation like 4-x=3) then they put it on the middle board.
My initial thought when I first started this activity was that it was too easy. I was wasting expensive sticky notes, and precious class time. But it was surprising how many students wrote equations that were in the wrong cloud or belonged on the middle board. A few students felt that subtraction and division were commutative and we had some great discussions about that property and how to solve those equations that they wrote. As I stood back and let the student discuss where the equations went, I heard a lot of great conversations that wouldn't have happened otherwise.
One suggestion, if you plan to hand out multiple sticky notes to your students, pre-disect them because it takes a lot of time to stand there and count out four stickies for each student.