X+6≠x, unless X ≠ x.
small x minus 6 would be equal to big X.
Let n be a side of the square. Then:
n²=36
n=√36=6 cm.
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Try this option (see the attacthed file; answer is marked with red colour); note, that

answer: 2 m/h.
We are given that ray CE is an angle bisector of angle ACD. With this, we have the equation,
mACE = mECD
Next, we look at the choices
<span>mECD = mECB > This not possible since ray CD is between the two angles
mACE = mACD > This is still not possible since ray CE is between the two angles
mACE = mDCB > This is possible since angles ACE, ECD and DCB are complementary angles.
mECD = mACD > This is not possible since ray CE is between the two rays
The answer is the third option</span><span />