Answer: 3
Explanation:
Since the phenotype ratio is 3 : 1, where red Roses are dominant over white roses, the ratio of red will be 3 while the white will be 1
Finding the value of the two roses will be;
3 + 1 = 4
For red roses,
3/4 × 4 = 3
For white rose,
1/4 × 4 = 1
Therefore, 3 of the red roses are there.