The problem seems to be involving a right triangle where the sides are represented by the lengths 10 in, 11 in, and x. To find the length x, you would typically use the Pythagorean theorem, which states that in a right triangle, the square of the length of the hypotenuse (the longest side) is equal to the sum of the squares of the lengths of the other two sides.
Assuming 11 in is the hypotenuse and 10 in is one of the other sides, the correct setup would be:
\[ x^2 + 10^2 = 11^2 \]
So the correct answer is:
x^2 + 10^2 = 11^2.