Final answer:
When crossing two violet petunias, it is most likely that 3/4 of the offspring will be violet, assuming violet is the dominant phenotype and that violet petunias have one dominant and one recessive allele based on Mendelian genetics.
Step-by-step explanation:
When two violet petunias are crossed, based on the given genetic information, the most probable result is that we will see a phenotypic ratio of offspring wherein 3/4 will be violet and 1/4 will be either blue or red. This is assumed from the description that suggests violet is a dominant phenotype resulting from a cross between red and blue petunias. According to basic Mendelian genetics, if violet (V) is dominant over red (r) and blue (b), and the violet petunias are a result of a blue and red cross, the violet petunias are likely to be heterozygous (Vb or Vr). A cross of two heterozygous violet petunias (Vb x Vb or Vr x Vr) would result in a 3:1 phenotypic ratio in the offspring.