Brynn is mowing the lawn. If it has taken 1/2 hour to mow 2/3 of the lawn, how long will it take to mow the entire lawn?

To mow 2/3 of the lawn, Brynn took 1/2 hour.

To mow 1/3 of the lawn, she took 1/2 hour * (1/2 / (2/3)) = 1/2 hour * (3/4) = 3/8 hour.
Thus, it will take Brynn (3/8) / (1/3) = (3/8) * (3/1) = 9/8 = <<9/8=1.125>>1.125 hours to mow the entire lawn. Answer: \boxed{1.125}.