The side b is called base of the right triangle, the 7 cm side is the height, and 13 cm is the hypotenuse. We can get the value of b by applying Pythagoras formula, which is b² + 7² = 13 ², and then b² =169 – 49 = 120, from where we get b= sqrt(120). Finally the true answer is A. V120 centimeters