What property of addition does the number sentence show?

3,050 + □ = 3,050

The square was supposed to represent the number zero... :/

geez - so why not just type 0?

The identity property of addition

similarly, for multiplication,
3,050 * 1 = 3,050

The number sentence is showing the property of addition called the identity property. This property states that when you add zero to any number, the sum is always the original number. In this case, the number sentence is representing that adding zero to 3,050 will result in 3,050.