find the length of side x to the nearest tenth.

Explanation:

Step1: Identify the triangle type

It is a right - triangle with two equal sides (isosceles right - triangle as indicated by the marks on two sides).

Step2: Apply Pythagorean theorem

For a right - triangle (a^{2}+b^{2}=c^{2}). Here (a = b=12), so (x^{2}=12^{2}+12^{2}). [x^{2}=144 + 144=288]

Step3: Solve for (x)

[x=\sqrt{288}\approx16.97]

Step4: Round to the nearest tenth

Rounding (16.97) to the nearest tenth gives (17.0)

Answer:

(17.0)