The cross between RrAa and RRaa genotypes represent a dihybrid cross because the genes of two traits are simultaneously being considered.
Since characters are not specified here, let's suppose that these are R represent dominant allele for seed shape Round while r represent recessive allele for seed shape wrinkled.
Similarly, A represent the dominant allele of flower color that is yellow while a represents the recessive allele of flower color that is green. (just supposing)
Let's cross them:
P1: RrAa x RRaa
gametes: RA: Ra : rA : ra X RA: Ra : rA : ra
Genotypic ratio
1/16: RRAA Round yellow
2/16: RRAa Round yellow
2/16: RrAA Round yellow
4/16: RrAa Round yellow
1/16: RRaa Round green
2/16: rrAa Wrinkled yellow
2/16: Rraa Round green
1/16: rrAA Wrinkled yellow
1/16: rraa Wrinkled green
You can see attached image for better understanding.
Hope it helps! :)