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 !