Let x = the cost of the Bug.
The cost of the Chevette is x + 3100
The cost of the Camaro is x + (x+ 3100) + 5000
The total cost of all 3 cars can be expressed as:
x + (x + 3100) + [x + (x + 3100) + 5000] = 31400
4x + 11200 = 31400
4x = 20200
x = 5050
The Bug cost $5050
The Chevette cost 5050 + 3100 = $8150
The Camaro cost 5050 + 5050 + 3100 + 5000 = $18,200