In a class of 100 students, there are 80 girls and 20 boys. twenty (20) are a students, and 12 of the a students are girls. if a student is chosen (only one student is chosen) from the class at random, what is the probability of choosing an a student, given that the student is a boy?

Two trains leave a station on different tracks. the tracks make an angle of 130°, with the station as a vertex. the first train travels 100 km and makes its first stop at point a, while the second train travels 200 km and makes it first stop at point b. how far apart are the trains when both are at their first stop? round the answer to the nearest integer. a) 65 km b) 139 km c) 224 km d) 275 km