When a triangle has angles 30°, 60°, and 90°, its side lengths are related to each other by a special ratio.
This ratio is such that the side opposite the 30°-angle is 1, the hypotenuse is 2, and the side opposite the 60°-angle is √3. This gives a ratio 1:2:√3.
Now, if we put in 7 for the side length opposite the 30°-angle, then the hypotenuse y must be 2 · 7, or 14, and the unknown leg x must be 7√3.
In sum:
,
.