The question states:
A very large number of Aedes mosquito larvae are on the surface of a river, scattered randomly so that the number of larvae is, on average, 3 per square cm. For a study of the spread of the Zika virus, A small net of area 2cm² is placed in the water and the larvae in that area collected.
Let T be the total number of larvae in four nets. What is the distribution of T?
Would T be $(3/cm^2)(2cm^2 * 4) = 24,$ or $(3/cm^2)(4 \text{nets}) = 12$?
Surely the size of the net matters, so your second guess is suspect.
I think your first guess is correct for the mean of the distribution. However, to answer the question you must also describe/name the distribution (and give reasoning).