Russell randomly surveys seventh-graders in his school and finds that 6 of 30 attend summer camp. If there are 200 seventh-graders in his school, how many are expected to attend summer camp?

There are 140 students in the seventh grade, and 5% are in the Environmental Club. How many students are in the Environmental Club?

In a hall, 50% of the 2100 students are boys. Some boys went to the field to pitch tents while the rest stayed in hall and prepared food. Of the students remaining in the hall, 30% were boys. How many boys went to pitch tents?

In Year 2, there are three times as many seven-year-olds as there are eight-year-olds. If there are 60 students in the year in total, how many of them are seven-year-olds?

On Thursday, 4 out of the first 10 students who ate a school lunch chose spaghetti. Based on this information, if 640 students ate a school lunch on Thursday, how many students could be expected to have chosen spaghetti?

A group of 75 students was surveyed about their preferred summer vacation activities. Out of these 75 students, 27 preferred swimming, 35 preferred boxing, and 28 preferred football. 10 of these students preferred exactly 2 out of the three activities. 5 students did not prefer any of these three activities meaning they could prefer to choose any, or all, or none at any point in time. What was the maximum number of students that preferred exactly one of these three activities?