Use a system of equations to solve this problem. Let "x" represent the number of classic cars, and "c" represent the number of cars.
320 = x + c
x = 4c
In this case, it'll be easiest to use the substitution method to solve the system of equations.
320 = (4c) + c
320 = 5c
Now solve for "c":
320/5 = c
c = 64
Since you now know there are 64 regular cars, you can subtract that from the total amount for the number of classic cars.
320 - 64 = 256
There are 256 classic cars.
To check the answer, multiply 64 by 4 and make sure it equals 256.
64 x 4 = 256
