Answer:

Explanation:
We want probability that 1st is girl AND 2nd is girl as well.
In probability "AND" means multiplication and "OR" means "addition".
We find the probabilities separately and multiply them together, since "AND".
- P(girl from 7th grader) = number of girl 7th grader/total number of 7th grader
=9/10
- P(girl from 8th grade) = number of girl in 8th grade/total number of 8th grader
=2/4
P(both girls) = 9/10 * 2/4 =9/20