To determine how many rosemary plants were planted, we first note that there are 4 different types of herbs planted: basil, thyme, rosemary, and oregano. The neighbors planted the same number of each herb.
Let's denote the number of each type of herb planted as \( x \). Since there are 4 types of herbs, the total number of plants can be expressed as:
\[ 4x = 52 \]
To find \( x \), we divide both sides of the equation by 4:
\[ x = \frac{52}{4} \]
Calculating that:
\[ x = 13 \]
This means there were 13 plants of each type of herb. Therefore, the number of rosemary plants is:
13 rosemary plants.
So the correct answer is: • 13 rosemary plants.