There is 192 pages in total and if she has read 30 pages already you need to work out how much is left so you do 192-30. That would be 162 pages. It says that she reads 18 pages a day so now you need to divide 162 by 18 pages to see how many days it will take for her to finish the book. that is how the answer is 9 days.
There are 105 in 6th grade because there are 75 boys right? So it said the ratio of girls is 7 and the ratio of boys is 5 so I divided 75 to 5 = 15 and I multiply 7 to 15 and got 105 girls.
