Please, Miss, is this correct? 

  81

-54

  33 

One possible response is: No. Below are other responses that you brainstormed. They go from those that are more centered on student-thinking to teacher-thinking (i.e. Who is identifying the student's error - the teacher or the student?)

Explain or defend your answer to me.

Tell me what you did.

What do you think? Tell me about each step.

How did you get that?

Tell me what you think.

Talk me through how you solved this.

What would you do if I said, “No”

Mohamed got 27. Discuss your work with him. (This strategy only works if Mohamed is not the one who always gets things right. There has to be room for either child to be correct.)

Is your answer reasonable?

Give me an estimate of the answer. (Follow up with Is it a little more than 30 or a little less than 30?)

How can you check your work?

Work with a partner to check it.

Could you work it out another way?

Please work out 84 – 51 for me and I’ll be back. 

Did you follow the subtraction rules?

Can you draw or model the answer for me?

How much more is $81 than $54? (Note: Two groups disregarded this question as not being helpful. Another group pointed out that it encourages the kids to add up to 81, i.e.  54 + 6  + 20 + 1 = 81, which would lead to checking via a second strategy. I thought this was a good point.)

Have you checked your work?

Check your work by adding.

Did you add to check?

Try checking with the inverse operation.

Can you show me this problem with manipulatives?

Does this question need trading (regrouping)?

You forgot to trade a ten for ten ones.

Add 54 + 33.

Did you check your answer by adding the 33 and 54?

Recheck your regroupings and explain your steps. 

What is 1 take away 4?

Hold up 1 finger. Can you take away 4?

What is the 8 in the problem?

Take another look at the ones column.