Jason bought 8 new baseball trading cards to add to his collection. the next day his dog ate half of his collection. there are now only 40 cards left. how many cards did jason start with

This is pretty  simple actually.

If they want how many cards before he added those 8 new ones then most likely 72 but seeming he ate half of his card and 40 isnt half of 72 we take 8+72 which equals 80. Add 40+40 or do 80/2 it comes out to be 40. So 80 cards to begin with.

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)