The missing length of the right triangle is 13.41 inches.
A right angle triangle has one of its angles as 90 degrees.
The side length of a right triangle can be found using Pythagoras theorem.
Therefore,
c² = a² + b²
where
Therefore,
x² = 18² - 12²
x² = 324 - 144
x² = 180
x = √180
x = 13.416407865
x = 13.41 inches
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