Answer:
There were 58 hardback books there.
Step-by-step explanation:
This question can be solved using a system of equations.
I am going to say that:
x is the number of paperback books.
y is the number of hardback books.
The number of paperbacks is 12 less than three times the number of hardbacks.
This means that:
![x = 3y - 12](https://tex.z-dn.net/?f=x%20%3D%203y%20-%2012)
Huong had 162 paperbacks.
This means that ![x = 162](https://tex.z-dn.net/?f=x%20%3D%20162)
How many hardback books were there?
We want to find y.
So, using the value of x, and the first equation, we have that:
![x = 3y - 12](https://tex.z-dn.net/?f=x%20%3D%203y%20-%2012)
![3y = x + 12](https://tex.z-dn.net/?f=3y%20%3D%20x%20%2B%2012)
![3y = 162 + 12](https://tex.z-dn.net/?f=3y%20%3D%20162%20%2B%2012)
![3y = 174](https://tex.z-dn.net/?f=3y%20%3D%20174)
![y = \frac{174}{3}](https://tex.z-dn.net/?f=y%20%3D%20%5Cfrac%7B174%7D%7B3%7D)
![y = 58](https://tex.z-dn.net/?f=y%20%3D%2058)
There were 58 hardback books there.