The answer is 5
Explanation:
The 9 by 15 picture is similar to the 3 by x picture, meaning its the same shape but not the same size.
Since we know what the width is for the first picture we have to get the width of the second picture to equal the same width without changing the shape.
To do that you divide BOTH 9 and 15 by 3
And you get 3 and 5.
Hope this help you understand better.
