Let x represent the number of chapters that Amy reads per hour. This is also known as the unit rate. We were told that Amy reads 2/5 chapters in 3/4 hours. Thus, we have the following equations
2/5 chapters = 3/4 hours
x chapters = 1 hour
By cross multiplying, it becomes
x * 3/4 = 1 * 2/5
3x/4 = 2/5
By crossmultiplying again, we have
3x * 5 = 4 * 2
15x = 8
x = 8/15
The unit rate in chapters per hour is 8/15