In topic 7, we worked on mental math strategies for addition and subtraction. I taught the class to circle the ones place (because ones starts with an O) and underline the tens place. This way, students make sure that they are adding the right numbers together when they can use mental math.
This strategy was also helpful in comparing numbers using <,>, and = symbols to help make sure that they are looking at the right number at the right time.
Another strategy that one of my co-workers showed me was using dots. For the greater than (>) symbol, you start by putting the two dots next to the bigger number and one dot by the smaller dot. Then you connect the dots.
This is a great strategy for students struggling knowing which way to point their arrows (if the alligator trick isn't working!).
Also in the Envisions program they teach how to subtract on a hundreds chart using addition. So when subtracting 74-58, you're supposed to start with 58 and then count over the ones until you're above the ones place of the first number and then count down the tens.
It was a difficult concept for students to get at first, but I think it is helpful in the long-term because it helps students see the relationship between addition and subtraction.