The missing side length is 6√5.
The given information suggests the use of the Pythagorean theorem, which states that in a right-angled triangle, the square of the hypotenuse c is equal to the sum of the squares of the other two sides a and b.
In this case, x is one of the legs, and 12 is the other leg, while 18 is the hypotenuse.
The Pythagorean theorem equation is:
![\[a^2 + b^2 = c^2\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/p01yqqswetzqhk18ka50n973aymiseg7f8.png)
In this context:
![\[x^2 + 12^2 = 18^2\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/339a84w1pzxthu5b3uq1hj8vg7fxbhelq1.png)
Now, solve for \(x\):
![\[x^2 + 144 = 324\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/ykgdquq6vaq8idg4cnwztgf6ubmae5zwlf.png)
Subtract 144 from both sides:
![\[x^2 = 180\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/bja6vvx90blxnp22e6hydhikte1e1g8dhw.png)
Take the square root of both sides:
![\[x = √(180)\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/76iztxua376zypv0o1qcuqnmhs76efh5ge.png)
Simplify:
![\[x = 6√(5)\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/om9rq5c7l1rp32akn7a1bpxhv4c8te8q3z.png)
So, the missing side length x is 6√5 inches.