Help me out with answe

I'll do better than that !  I'll show you how to do it, because
the answer is no help if you don;t know how to work it out.

Do you see that little square in one corner of the triangle ?  That tells you
that the angle there is 90 degrees, and THAT tells you that the triangle is
a  RIGHT triangle.  This is a very helpful piece of information, because there's
a rule about the sides of  a right triangle that isn't true for any other kind of triangle. The rule is:

             (the longest side)² = (one of the other sides)² plus (the third side)²

Also, the longest side is always the one that doesn't touch the 90-degree angle.

In this triangle in the picture,

-- the longest side is 'A' ... it's 13 .
-- one of the other sides is ' b ' ... it's 12 .
-- the third side is ' C ' ... the one you have to find.

Using the formula up above, you know that      

             (13)² = (12)² + C²

Before you go to work on it, subtract (12)² from each side of this equation,
just to make it a little easier, and then you have      

         C² = (13)² minus (12)²

And right there is how to figure out the length of ' C '.

I'll give you even more information to help you, and then it's up to you
to finish it and get the answer.  Here it is:

       (13)² = 169

       (12)² = 144

Now you have everything you need.  Go to it !

To get the answer we can use Pythagorean theorem.
    /-144
- its the answer