To find the ratio of carnations to the total number of flowers in the bouquet, first calculate the total number of flowers.
Total number of flowers = Number of roses + Number of carnations = 7 roses + 13 carnations = 20 flowers.
Next, the ratio of carnations to the total number of flowers is:
Ratio of carnations to total flowers = Number of carnations : Total number of flowers = 13 : 20.
Therefore, the ratio of carnations to the number of flowers is \( \frac{13}{20} \) or 13:20.