In simple dominance, what is the result when a dominant allele pairs up with a recessive allele?

According to Mendel's law of dominance,

in such a situation the dominant allele is displayed externally while the recessive allele remains masked i.e, the recessive remains in the genotype along with the dominant allele while in its phenotype, only dominant remains.

Idon't know how to do this but maybe ask your mom or dad