Let \( x \) be Judy's hourly rate and \( y \) be Ben's hourly rate.
From the information given, we can set up the following equations based on their hours worked and their combined pay:
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For the first situation (Judy worked 8 hours and Ben worked 10 hours), we have: \[ 8x + 10y = 80 \]
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For the second situation (Judy worked 9 hours and Ben worked 5 hours), we have: \[ 9x + 5y = 65 \]
Now we have the system of equations:
\[ \begin{align*}
- & \quad 8x + 10y = 80 \quad \text{(1)} \
- & \quad 9x + 5y = 65 \quad \text{(2)} \ \end{align*} \]
To solve these equations, we can first simplify equation (1) by dividing everything by 2:
\[ 4x + 5y = 40 \quad \text{(3)} \]
Now we have:
\[ \begin{align*} 3) & \quad 4x + 5y = 40 \ 2) & \quad 9x + 5y = 65 \ \end{align*} \]
Next, we'll eliminate \( y \) by subtracting equation (3) from equation (2):
\[ (9x + 5y) - (4x + 5y) = 65 - 40 \] \[ 5x = 25 \] \[ x = 5 \]
Now that we have \( x \), we can substitute \( x = 5 \) back into equation (3) to find \( y \):
\[ 4(5) + 5y = 40 \] \[ 20 + 5y = 40 \] \[ 5y = 20 \] \[ y = 4 \]
Thus, Judy's hourly rate is \( \boxed{5} \) dollars per hour, and Ben's hourly rate is \( \boxed{4} \) dollars per hour.