Why were pops singled out for regulation by the international community?

 The correct answer is :  Because persistent organic pollutants are chemical substances that persist in the environment, they do not decompose easily and can travel long distances. They represent a risk to the environment and to human health. They are formed by pesticides, by industrial chemicals and byproducts of industrial processes.

i really dont know the answer

answer: this problem has only trivial solutions, with all points on the same line. x=5 or x=7/5.

step-by-step explanation:

there are three triangles, and three unknowns: x, y=length of middle segment, and z=cos(angles marked with red arc).

we need

and law of cosines,

the three equations are

see attached image for solution.