For these types of questions with sin cos or tan, you will need to use a calculator. There is no other way as far as I have seen on the internet to solve this type of problem. Anyways, what you have to do is take your calculator and put in:
sin
sin(2/3+3/5) exactly like that
and the calculator will give this to you:
0.022105703 which you can then round up.
I hope this answer helped you out. If it did I would greatly appreciate it if you could check out my channel The Game Rater(or Nitro Studios the name might change). I would really appreciate that. Thanks.