1/3 (0.333,,,) is 0.05666... away from 0.39 .
2/5 (0.4) is 0.01 away .
3.8 (0.375) is 0.015 away .
9/25 (0.36) is 0.3 away .
2/5 is the closest one.
Not sure what you're asking. are you wanting to solve 5 ( a - b), where b equals those two things listed below? If that's the case, I can definitely help. If not, please clarify.
The length side of AD is 4 units