An apple plant has two dominant alleles for red apples, rr, which, percentage of the offspring will have red apples, assuming random chromosome segregation?

A dominant allele would be RR or Rr. And a recessive allele would be rr. The question is a bit unclear.

If you create a Punnett Square, the percentage of offspring that will have red apples would be 50%. Since there would be two dominant and two recessive alleles.