Let r be the rate of Hannah can play songs each hour.
If she can play 4 songs in 2/3 hr
r = 4 songs/(2/3) hr = 12/2 = 6 songs/hour
For the total number of songs in a given amount of time, we use the equation
t (time in hours) * r (rate of song playing) = n (number of songs)
If t = 1 hr, r = 6 songs/hr, and t*r = n, n = 6