8 find the missing length

Answer:
C) 15m
Step-by-step explanation:
Since this is a right triangle (we know this since the box in the top left of the image shows that angle is 90°) We can use the pythagorean theorem.
formula for the pythagorean theorem = a² + b² = c²
The easiest way to think about this is to just know that the long side (our missing side in this case) is "c."
So, we plug our numbers in: (it doesn't matter which legs of the triangle you use for "a" or "b")
9² + 12² = x²
9² = 81
12² = 144
81 + 144 = 225
now we know the missing side (squared) is 225. All we need to do is just find the square root ([tex]\sqrt[/tex]) of 225.
[tex]\sqrt{225}[/tex] = 15
15 is your answer.