Subtraction and division (the negative operations) are very difficult for kids to understand. Multiplication (also called multiple addition) is much easier for them to understand.
We used popsicle sticks in bands of ten so we had tens and ones. This worked very well for subtraction.
Teaching your child the "words" in word problems helps. Two-stage problems are more difficult. They should draw a picture for these. Drawing a simple picture should go all the way through Calculus and above. Math Professors always begin by drawing a picture and I think that is their main trick. In fact, I assign my class to just draw the picture and not bother with working the problem until they get this concept.
For some reason, in our society, this is supposed to end at a young age, but it develops them for the more advanced math. Calculus is full of these and I had to learn quickly how to do it.
