When you cross two hybrids, the results always come in a 3:1 ratio as follows:
3 is the inheritance of at least 1 dominant allele
1 is the inheritance of two recessive alleles
Punnet Squares are very useful!
T t
T | TT | Tt |
t | Tt | tt |
Three out of 4 boxes have offspring that express the dominant trait (tall plants) and 1 out of 4 boxes expresses only the recessive trait (short plants).
Hope this helps! :)