Let's denote the price of a hot dog as \( h \) and the price of a soft drink as \( d \).
From the information given, we can set up the following equations based on the purchases:
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For Jamie: \[ 6h + 4d = 13 \]
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For Amy: \[ 3h + 4d = 8.50 \]
Now, we have a system of equations:
\[ \begin{align*} 6h + 4d & = 13 \quad \text{(1)} \ 3h + 4d & = 8.50 \quad \text{(2)} \end{align*} \]
To eliminate \( d \), we can subtract equation (2) from equation (1):
\[ (6h + 4d) - (3h + 4d) = 13 - 8.50 \]
This simplifies to:
\[ 3h = 4.50 \]
Now, we can solve for \( h \):
\[ h = \frac{4.50}{3} = 1.50 \]
So, the price of a hot dog is \( \boxed{1.50} \).