H̲̅ᴇ̲̅ʏ̲̅! Hope that I can help!
To do this, we need to put it into an equation. This equation is

. To find out what

is we need to subtract the 8 from both sides of the equation to make it even. 8+

-8=

. 15-8=7.

=7. Becuase

represents 2 cards, we need to divide it by 2. 7÷2=3.5.
He can spend $3.50 for each card.
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