Step-by-step explanation:
It is given that,
Speed of sound, v = 750 miles per hour
Since, 1 miles/hour = 1.46 foot/second
So, the speed of sound, v = 1100 feet/second
It takes about 3 seconds to hear the echo, t = 3 seconds. Let the canyon wall is d feet away. It can be calculated as :
![d=v* t](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5saovervhbexg664fxszt3uynixwo2lgpl.png)
![d=1100\ ft/s* 3\ s](https://img.qammunity.org/2020/formulas/physics/high-school/hwzao63royhnthng56w35bo3j2a0bwrovr.png)
d = 3300 feet
Echo is the repetition of sound. So, the canyon wall is 3300/2 = 1650 feet away. Hence, this is the required solution.