Use the Pythagorean theorem to find a whole number estimate of the length of the unknown side of the right triangle. The length of the unknown side of the triangle is approximately cm.

12 cm

Step-by-step explanation:

Leg of one side  = 5 cm

Hypotenuse = 13cm

According to the theorem,

   A^2 + B^2 = C^2

   5^2 + B^2 = 13^2

   25 + B^2 = 169

Subtract 25 form both sides,

    B^2 = 169 - 25

     B^2 = 144

     B = sqrt( 144 )

      B = 12

Done!

the correct answer is the second option