Anything with a dotted line represents subtraction.

1, this is a subtraction problem, because there is a dotted line, but it is not clear which side to remove, so two subtraction formulas are usually written. The subtraction formula must first count the total, and then subtract the left part to get the right part 6-2 = 4; Subtract the right part from the total to get the left part 6-4=2.

2. This is a subtraction problem, because it is clearly stated that both the dotted line and the diagonal line mean to take away, and the part of hueco mundo and the part crossed out by the diagonal line mean to remove a part from the total. In this case, only one formula can be written, but it must be emphasized that the total number of objects must be reduced, and students can easily write the taken part with the remaining part. The formula should be: 10-4=6.