Answer:
We're solving for CD. If we look at ΔABD we notice that it's a 30-60-90 triangle which has a side length ratio of 1:√3:2 and in this case the 1 is 300 so side BD = 300√3. Similarly, ΔABC is also a 30-60-90 triangle but this time the √3 is 300 so side BC = 100√3. We know that CD = BD - BC using PWP so the answer is 300√3 - 100√3 = 200√3 = 346.4 feet.
