−8,−12,−16, find the common difference or common ratio.

I'm terrible at math any here is appreciated.

Elena and her husband marc both drive to work. elena's car has a current mileage (total distance driven) of 15,000 and she drives 23,000 miles more each year. marc's car has a current mileage of 46,000 and he drives 9,000 miles more each year. will the mileages for the two cars ever be equal? explain.

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?