Johnny mows 6 yards in 1 hour, and he has 21 yards to mow. how long will it take him?

This is a proportion equation. 6 yards in 1 hour is 21 yards to x hours. 

x=hours it takes to mow 21 yards

1) Set up your proportion: 6 yards / 1 hour = 21 yards / x hours
2) Now you cross multiply.  (6*x)=(1*21)
3) 6x=21
4) Divide both sides by 6
5) x=3.5

So Johnny can mow 21 yards in 3.5 hours.

Hope this helps!  :)

He na a