Seems like for this question we really have to take sin inverse of 3/4 and sin inverse of 1/4 for part b to get the values of x + y and x - y

Brilliant! How do u get these ideas. I envy u

In the usual sense the question would not ask you to find the relevant angles, but this time they really asked you to find x and y. This gives an indication that you have to take the inverse sine. There is no other way to solve this question.

I spent so much time wondering how to solve. U did it so quick