Let the cost of each of the first 3 tires be \( x \). The cost of the 4th tire is $5.
The total cost can be represented by the equation: \[ 3x + 5 = 237.50 \]
Subtract 5 from both sides: \[ 3x = 237.50 - 5 \] \[ 3x = 232.50 \]
Now, divide by 3 to find \( x \): \[ x = \frac{232.50}{3} = 77.50 \]
Thus, the cost of each of the first 3 tires is $77.50.