Trait X is dominant to x. if you cross a homozygous dominant parent with a heterozygous parent, what is the chance that the offspring will express the recessive trait?

50% chances

Explanation:

Here trait X is dominant to x, so alleles of homozygous dominant parent will be XX and alleles for heterozygous parent will be Xx.

When homozygous dominant parent will be crossed with heterozygous parent, the result will be XX, XX, Xx and Xx. There are total four offspring out them two offspring express the recessive trait.

Hence, there are 50% chances that the offspring will express the recessive trait.