Let \( x \) be the cost of a tray of club sandwiches, and \( y \) be the cost of a tray of vegetarian sandwiches.
We can set up the following system of equations based on the information given:
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For the first order (4 trays of club sandwiches and 4 trays of vegetarian sandwiches with a total cost of $72): \[ 4x + 4y = 72 \]
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For the second order (1 tray of club sandwiches and 4 trays of vegetarian sandwiches with a total cost of $42): \[ 1x + 4y = 42 \]
Now, we can simplify the first equation by dividing everything by 4: \[ x + y = 18 \quad (1) \]
Now we have the simplified first equation (1) and the second equation:
- \( x + y = 18 \)
- \( x + 4y = 42 \)
Next, we can solve the system using substitution or elimination. Here, we will use substitution. From equation (1), we can express \( x \) in terms of \( y \): \[ x = 18 - y \quad (2) \]
Now substitute (2) into the second equation: \[ (18 - y) + 4y = 42 \]
Combine like terms: \[ 18 + 3y = 42 \]
Now, isolate \( y \): \[ 3y = 42 - 18 \] \[ 3y = 24 \] \[ y = 8 \]
Now, substitute \( y \) back into equation (2) to find \( x \): \[ x = 18 - 8 \] \[ x = 10 \]
Thus, the cost of a tray of club sandwiches is \( x = 10 \) dollars, and the cost of a tray of vegetarian sandwiches is \( y = 8 \) dollars.
A tray of club sandwiches costs $10, and a tray of vegetarian sandwiches costs $8.