Dan started with 69 cards
Step-by-step explanation:
Let x be the initial number of cards
Then
According to "Dan bought 7 new baseball trading cards to add to his collection"

The next day his dog ate half of his collection.

There are now only 38 cards left.

Multiplying both sides by 2

Subtracting 7 from both sides

Hence,
Dan started with 69 cards
Keywords: Linear equation, word problems
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Answer:
C is the answer
Step-by-step explanation:
10x=180-140
so,x=40÷10=4answer
Divide by 21 to put the equation in intercept form.
x/(21/9) + y/(-21/7) = 1
x/(7/3) + y/(-3) = 1
The x-intercept is (7/3, 0)
The y-intercept is (0, -3)
The 3rd choice is appropriate.