Answer:
0%
Step-by-step explanation:
According to the question, the inheritance pattern of flower colour in four o'clock plants follow incomplete dominance i.e. one allele is not completely dominant over the other, and instead they form a heterozygous plant with a third intermediate phenotype (flower colour).
In this case, a four o'clock plant with genotype RR will have red flowers while a plant with genotype rr will have white flowers, Hence, they cross to form an all Rr genotype offsprings with pink flowers (since the red allele is incompletely dominant). Therefore, the percentage chance of having a red flower offspring from this cross is 0%, as it cannot occur.