For exactly 2 plants to not grow, that means 7 do grow. The probability of an individual plant growing is p=0.9. Conversely the probability of an individual plant not growing is q=1-p = 0.1. The probability of exactly k successes in n trials, where the probability of the success of any one trial is p and the probability of failure on any one trial is q=1-p, is given by the Binomial Probability Formula:

Here p = 0.9, q=0.1, k = 7, and n=9.

Can you take it from here? What do you get for a final answer?