Answer:
Proof for 
Step-by-step explanation:
We are given that a, n, b, r and k are integers.
Also,

Since k divides a and b, we can write,
a = rk and b = sk, where r and s are integers.
Now, we have to prove that k divides r as well that is 
Putting value of a and b in the equation, we get:

Since, (r-sn) is an integer, k divides r.
Answer:
66.4°
Step-by-step explanation:
To find the angle XYZ, we are to use sine rule. For this, we have to first find ∠Z.
Given that: ∠X = 90° (right angle), XY = 6 cm, YZ = 15 cm. Hence:

∠X + ∠Y + ∠Z = 180° (sum of angles in a triangle)
90 + ∠Y + 23.6 = 180
113.6 + ∠Y = 180
∠Y = 180 - 113.6
∠Y = 66.4°
∠Y = ∠XYZ = 66.4°