Benny brought five new baseball trading cards to add to his collection. the next day his dog ate half of his collection. there are now only thirty cards left. how many cards did benny start with? Pls show work and the check too.

Benny started with 55 five cards. In order for his dog to have eaten half his cards and end up with 30 cards, that would mean he had 60 cards. Mind you, he had bought 5 more the day before his dog ate them. I hope that makes sense

He started off with 55 cards

The property is commutative property of addition ⇒ 3rd answer

Step-by-step explanation:

* Lets explain the commutative property of addition

- The commutative property of addition means changing the order

 of the numbers we are adding without changing the result of adding

- Ex: 2 + 1 + 3  can be written as  3 + 2 + 1 without changing the sum

 of the numbers

* Lets solve the problem

- We want to use the mental computation to simplify the problem

  27 + 15 + 3 + 5

∵ It is easy to find the sum of 27 and 3

∵ It is easy to find the sum of 15 and 5

∴ We want to re-arrange the places of the numbers

∴ 27 + 15 + 3 + 5 could be written 27 + 3 + 15 + 5

∵ The sum of 27 + 15 + 3 + 5 = 50

∵ The sum of 27 + 3 + 15 + 5 = 50

∴ There is no change in the result of the addition

∵ The commutative property of addition means changing the order

  of the numbers we are adding without changing the result of adding

∴ The property is commutative property of addition