Two internationally-renowned rock climbing areas have limestone rock. El Chorro is in mainland Spain, and has a dry climate with little precipitation. Tonsai is a beach on the coast of Thailand; here, the rock is constantly exposed to moist, salty air. Which of these climbing areas is known for having fragile rocks that can break and endanger climbers?

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference. 

The answer to the question is c.

Joe ran 130 yards because 3 feet make 1 yard so using this ratio 390 feet make 130 yards.