$\"\"$

Speed = $\"\"$ Substitute distance = 3 miles and times = 6 seconds

Speed = $\"\"$ \ \ $\"\"$

1 hour = 60 minutes

1 minute = 60 Seconds

So, 1 hour = 60 × 60 Seconds

1 hour = 3600 seconds $\"\"$

Speed = $\"\"$

Speed = $\"\"$ × $\"\"$

Speed = $\"\"$ × $\"\"$ (Cancel out common unit seconds)

Speed = $\"\"$ × $\"\"$

Speed = $\"\"$ $\"\"$

Simplify, Speed = $\"\"$

Speed = 1800 miles per hour

$\"\"$

The speed is 1800 miles per hour.