Punnett square problem?
First of all this is a monohybrid cross because you are dealing with one trait: the color of the flowers, for which you have two phenotypes or physical expression. The genotype is actual set of genes that an organism carries versus the phenotype which is what is seen on the plant.
Assuming that both the plants start off as a homozygous for their traits you get a RR x rr.
(“R” will be red and “r” will be white)
when you cross them you will get Rr, Rr, Rr, & Rr. Because R is dominant, any of the four possibilities containing a “R” will be red. So for your F1 the phenotype is 100% red or 4 red: 0 white, and the genotype is 0RR:4Rr:0rr.
for F2, you would a cross of two heterozygous plants. Rr x Rr
when you cross the two plants you would get: RR, Rr, rR, rr
Phenotypic ratio is 3red : 1 white
Genotypic ration is 1RR: 2Rr: 1rr