SQUARES BECAUSE THEY ARE IN THE MIDDLE DUMMY
Here's my interpretation: 4 whole km, plus zero tenths of a km, plus 3 hundredths of a km, plus 5 thousandths of a km.
X is 9
12x + 17 = -1 + 14x
18 = 2x
x = 9
Since it is a square, the diagonals are congruent. If a square is split like this, it becomes two congruent right triangles. The relationship between the sides and hypotenuse is a 1:

ratio. So if the diagonal of a square is 14 cm, then the side length would be 14/

, which is approximately 9.899. I don't understand what the answer choices are, but you should be able to square root the numbers to determine the answer.