HELP

Use the Pythagorean Theorem.

a^2+b^2=c^2 is the formula.

Since a=5

          b=12

We can plug these values in.

5^2+12^2=c^2

25+144=169 (or c^2)

the square root of 169 will get us 13.

Hence, the third side length is 13 units.

Hope this helped!

If the '12' side could be the hypotenuse, then there is another answer:

Let  a = 5  and  c = 12:     a² + b²  =  c²

                                       (5)² + b²  =  (12)²

                                         25 + b²  =  144

                                                  b²  =  119

                                                    b  =  sqrt(119)