One strategy I worked out with subtraction is the fingers, it helps me count backwards so that I see that it's being taken away. I'll start at ten or any other number with my thumb and count back. I just have to really pay attention to what I'm doing. It's a little frustrating, though. Another strategy I like to use is drawing pictures or tally marks. Once again, it helps me actually see the numbers being taken away. These strategies could help you to if you learn by doing something or seeing something.