The traits here are codominant, as the combination of red and white alleles in the first snapdragon leads to a phenotype of a combination of red and white: pink.
Punnet squares are great for questions like these:
R W
R| RR | RW |
R| RR | RW |
1/2 of the boxes are of the genotype RR, and half are RW. This means that 1/2 of the offspring will be RR (red), and 1/2 will be RW (pink).
Hope this helps! :)