To represent the problem mathematically, you can set up the equation based on the information provided. The total number of candy flowers \( f \) in the bag is divided equally among 6 students, with each student receiving 3 candy flowers.
The equation can be modeled as follows:
\[ \frac{f}{6} = 3 \]
To solve for \( f \), you can multiply both sides of the equation by 6:
\[ f = 3 \times 6 \]
Calculating the right side gives:
\[ f = 18 \]
So, the number of candy flowers in the bag to start was \( \boxed{18} \).