Answer:
A: 15
Step-by-step explanation:
It is asking for the hypotenuse of the triangle. To find this, use pythaogreans theorem.
A^2 + B^2 = C^2
In this case,
9*9 + 12*12 = C*C
81 + 144 = C*C
225 = C*C
Now do the square root of both sides and you get
15 = C. Therefore the missing length is 15.
