a person, with his ears to the ground, seconds a huge stone strike the concrete pavement. a moment later two sounds are heard from the impact, one travels in the air and other in the concrete, and they are 0.80 seconds apart. How far away the impact occur?

Answer 1

I do not understand "seconds a huge stone"

Answer 2

Me either but you'll have to compare the speed of sound to the speed of sound in concrete.