Most of the time, it is because they need the military aid or the resources that a certain country needs. That's kinda what the UN is all about is aiding each other in times of war
You can use the cos ratio to find the value of x. Since we know cosine is adjacent/hypotenuse, we can do cos(60)=x/40. Then, we multiply each side by 40 to find the value of x. So, x=20.