Remember,
sin = op/hyp
cos = adj/hyp
tan = op/adj
For question 3 it would be B and C, because the adjacent side of angle x is 12, the hypotenuse is 37, and cos = adj/hyp. Also, the opposite side of angle z is 12, and the hypotenuse is 37, and sin = op/hyp. So both answers would be 12/37. You would do the same with question 4.
For 5, you would do the same thing. It would be D because you can only take the sin of angle 24, and x is a side. the opposite of 24 is x and the hypotenuse is 11, so sin 24 would be x/11. It is the same for problem 6.