In certain species of roses, white roses and red roses are incompletely dominant to each other. when a red rose and a white rose are crossed, a pink rose is produced. what is the probability of producing a white rose when a red rose is crossed with a pink rose

The answer is 0%.

If white and red roses are incompletely dominant, the phenotypes are as following:

AA - red roses

AB - pink roses

BB - white roses

So, a cross between a red (AA) and a pink rose (AB) will result in only red or pink roses:

Parents: AA x AB

Offspring: AA AA AB AB