Final answer:
The height of the bookmark is 15 centimeters.
Step-by-step explanation:
To find the height of the bookmark, we can use the formula for the area of a rectangle which is length times width.
In this case, the area is given as 45 square centimeters and the width is 3 centimeters.
Let's use the variable 'h' to represent the height. So, we have the equation:
3h = 45
To solve for 'h', we can divide both sides of the equation by 3:
h = 15
Therefore, the bookmark is 15 centimeters tall.