Final answer:
The length of BC in the right triangle with sides 9 and 12 is 15.
Step-by-step explanation:
In a right triangle, the length of the hypotenuse can be found using the Pythagorean theorem, which states that the square of the hypotenuse is equal to the sum of the squares of the other two sides.
In this case, the lengths of the other two sides are given as 9 and 12. Let's label the hypotenuse as BC. We can use the Pythagorean theorem to solve for BC:
a2 + b2 = c2
92 + 122 = c2
81 + 144 = c2
225 = c2
Taking the square root of both sides, we find that the length of BC is 15 units.