When did Nam start to do karate? => How long is

Cách 1:
- How long has Nam been practicing karate?
- Nam started to do karate a year ago.

Cách 2:
- How long has Nam been training in karate?
- Nam began his karate training last summer.

Cách 3:
- When did Nam first start learning karate?
- Nam has been practicing karate for two years now.

Nam has been doing karate since he was in grade 7.

Nam took up karate classes in his second year of junior high school.

Nam began practicing karate in 2018.

Nam started to do karate 3 years ago.