Final answer:
Kristen has a total of 54 milliliters of syrup.
Step-by-step explanation:
To find the total volume of syrup Kristen has, we need to multiply the number of containers by the volume of syrup per container. In this case, Kristen has 9 containers and each container contains 6 milliliters of syrup. So, the total volume of syrup Kristen has is 9 containers x 6 milliliters/container = 54 milliliters.