This activity is about adding and subtracting positive and negative numbers.
Adding
181 + 431 = 594
-464 + 445 = -19
Remember that -464 + 445 is the same as 445 - 464
Subtracting
420 - 421 = -1
-160 - 160 = -320
Think of a number line if it helps. When you subtract, you move to the left to make a number more negative.