1)
12 km
12 km
20 km
Is it a right triangle?

No, it is a obtuse triangle instead

Step-by-step explanation:

So, you use pythagorean and theorem which is a^2 + b^2 = c^2

So when you plugin in the numbers, it's 20^2__ 12^2 + 12^2

When you square them you get left with 400__144 + 144

Then, you add 144 + 144 = 288

But since 400 is > than 288, then it's an obtuse triangle.

No

Step-by-step explanation:

It does not follow the Pythagorean Theorem, which states that the two shorter sides squared (squared BEFORE added together).  12 squared is 144, and 144 plus 144 equals 288.  20, which seems to be the hypotenuse, squared is 400.  288 does not equal 400.