I don't understand how to do these problems very well..

I'll type out what i did so far if i tried..

15sin^2x-26sinx+8=0

sinx(15sinx-26)+8=0

16sin^3x-12sin^2x+26sinx-27=0

4sin(4sin^2x-3sinx)+9(4sinx-3)=0

(root2 sinx+1)(3tan3x-root3)=0

sin 3x=-root2/2

for this one, i don't know what to do with the 3x. I heard that there is supposed to b 6 answers when the multiple of the angle is 3, but how do i find this?

If I have more trigometric equations problems, should I update this thread, or just start a new one?