Consistently, every single one of my 1st and 2nd grade students has had difficulty with addition problems where one addend is missing. 4 + ? = 10. ? + 3 = 7. They just could not "get" that the answer was given to them.
I would pull out blocks. "The answer is 10," and I would show ten blocks. I would separate the blocks into two piles. "You have 4 blocks. How many more blocks do you add to get ten?" I would point to the other pile. The student would count the blocks and write down the correct answer. Then I would try the next problem. "The answer is 7," and I would show a pile of 7 blocks. This time I would not divide the blocks into the correct piles. "You have 3 blocks. How many more do you need to make 7?"
I tried examples and other manipulatives. "There are 10 superheroes. 4 have eaten lunch. How many more need to eat lunch?"
"There are 7 little ponies. 3 are in the stable. How many more need to get in the stable for bedtime?"
More blank stares. And lots of frustration on both sides.
Jenny has reached this stage in her math. Most lessons include this sort of problem. We've been having some tense moments. Fortunately, I remembered today the one example that has worked flawlessly with every single child thus far.
"It is Billy's 10th birthday. I am putting the candles on his cake. I put 4 candles on but then I have to go clean up a mess that Mary made. How many candles do I have left to put on the cake?" I used colored pencils and demonstrated the problem. I could see the light bulb going off right away. As I walked away, I could hear her saying, "It's my 7th birthday. I put 3 candles on the cake. How many candles are left to put on the cake?" When I returned a few minutes later, the problems were finished. Each one was correct.
No more blank stares. Hooray!