Oh wait I read the question wrong, give me 5 minutes lol. Edit: Nvm, I read it right :). This is the answer.
Answer:
3:2
Explanation:
1 hour and 15 minutes can be seen as 75 minutes so it would be
75:50
The highest common mutiple of 75 and 50 are 25. Divide both (75&50) by 25.
The answer would be 3:2