`1.` I need to work hard so I want to pass the exam.

- BecauseI want to pass the exam I need to work hard.

- because: bởi vì

- so: vì vậy

`2.` He was the best candidate so he easily won the race.

- He easily won the race because he was the best candidate.

- because: bởi vì

- so: vì vậy

`3.`However she went to the shop, she couldn't find anything she liked 

- Although she went to the shop, she couldn't find anything she liked.

- However + S + V = Although + S + V

because: vì

so: vì vậy, nên

1. Because I want to pass the exam, so I need to work hard. (Vì muốn thi đỗ nên tôi cần phải cố gắng nhiều.)

I need to work hard because I want to pass the exam. (Tôi cần phải làm việc chăm bởi vì tôi muốn vượt qua kỳ kiểm tra.)

2. Because he was the best candidate so he easily won the race./ Because he easily won the race so he was the best candidate (câu này có thể viết = hai cách đều đúng, Vì là thí sinh giá nhất nên anh ấy dễ dàng chiến thắng trong cuộc đua./ Vì anh ấy dễ dàng thắng cuộc đua nên anh ấy là thí sinh sáng giá nhất.)

3. Although she went to the shop, she couldn't find anything she liked.

However she went to the shop, she couldn't find anything she liked.

Although: mặc dù

However: tuy nhiên