A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR).
What percentage of the offspring will be homozygous dominant (RR)?

So I don’t see answer choices here, but your answer is 50% of the offspring will be homozygous dominant with RR, and 100% of them will carry a homozygous dominant gene of Rr

If you take the two sets and put them into a punnett square, it would look like this (image attached):

When the two sets of alleles are crossed, you would end up with half of your pairs being fully dominant (RR), and the other half being dominant while containing a recessive gene (Rr). Since there’s only one recessive gene in these pairs, it gets overridden and the pair itself is dominant.

So your answer is 50% will be homozygous dominant with RR!