To find the length of segment HE, we can apply the property of intersecting chords in a circle. When two chords intersect inside the circle, the products of the segments of each chord are equal.
Given:
- FE = 12
- EG = 7
- EK = 21
- Let HE = x
According to the property of intersecting chords, we have:
\[ FE \cdot EG = HE \cdot EK \]
Substituting the values:
\[ 12 \cdot 7 = x \cdot 21 \]
Calculating the left side:
\[ 84 = x \cdot 21 \]
Now, divide both sides by 21 to solve for x:
\[ x = \frac{84}{21} = 4 \]
Thus, the length of segment HE is 4 units. The correct choice is:
Segment HE is 4 units long.