Cuál sería la contestación?

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.

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9