Jason bought 7 new baseball trading cards to add to his collection. The next day half of his collection. There are now only 30 cards left.

8 cards

Step-by-step explanation:

Work Backwards:

30/2 is 15

15-7 is 8.

Hope this helps :D

Step-by-step explanation:

Let x be the number of cards Jason had initially in his collection.

"Jason bought 9 new baseball trading cards to add to his collection"

x

+

9

is the equation because  

x

is the initial number of cards he has and he bought another 9

"His dog ate half of his collection"

1

2

(

x

+

9

)

because  

x

+

9

is what he had before his dog ate his cards and since his dog ate half, there is a  

1

2

added to the equation

"42 cards left"

1

2

(

x

+

9

)

=

42

Since his dog ate half, he is left with half of his initial card collection.

x

+

9

=

42

×

2

x

+

9

=

84

x

=

84

−

9

x

=

75

mxb67

step-by-step explanation: