A group of girls stood in three rows. The 1st row had 10q girls. The 2nd row had 7q fewer girls than the 1st row. The 3rd row had 4 more girls than the 2nd row.
- Find the number of girls in the 3rd row in terms of q. Give your answer in the simplest form.
- There were 13 girls in the 3rd row. Find the value of q.