The answer is 5.23 ft/second
The way I got this answer was first finding the circumference of the merry-go-round using the equation

, where r represents the radius, which is the distance from the center of a circle.
So your equation should look like this

. I used the rounded term of 3.14 for

Once you multiply those terms, you should get the answer, 31.4. Now this is the total distance around the merry-go-round in feet. So, if it takes 6 seconds to make a full rotation and we are trying to find the amount offeet traveled in one second, we should divide the circumference (31.4) by 6 to give us our answer.
So, 31.4÷6=5.2333...ft/second
And I rounded the answer to the nearest hundredth to get 5.23 feet/second