If i had $15 in 1983 what would be the equivalent of that amount today due to inflation?
If you’re looking for an average based on a basket of goods, Ringo’s number is probably what you want.
On the other hand, if you just want to fill up your car, this site Historical Yearly California Gasoline Prices per Gallon says that you could buy a little over 13.4 gallons of gas with your $15 back in 1983.