In a monohybrid cross, if the gene for tall (t) plants was incompletely dominant over the gene for short (t) plants, what would be the predicted result of crossing two intermediate (tt) parent plants? (hint: you may want to complete a punnett square.)
25 percent tall, 50 percent intermediate, 25 percent short
50 percent tall, 25 percent intermediate, 25 percent short
100 percent intermediate 25 percent tall, 75 percent intermediate

Incomplete dominance is when the dominant allele is not fully dominant over the recessive allele. This results in three phenotype options rather than three. in this case T= tall, t= short and the two combined would be an intermediate height. A punnet square can help you figure this out.
         T     t
T      TT    Tt
t       Tt      tt

In this case you have one genotype that is two tall (TT) alleles. This will present as a tall plant.
The second genotype present is two  short alleles (tt). You have one of these that will result in a short plant.
The third genotype present is one of each (Tt). This will result in an intermediate height plant. This shows up twice in the punnet square.
Based on this you will have 25% tall, 25% short and 50% intermediate.