Math question, i appreciate any ! : )

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

65% of students in your school participate in at least one after school activity. if there are 980 students in you school, how many do not participate in an after school activity?

Okay so i didn't get this problem petro bought 8 tickets to a basketball game he paid a total of $200 write an equation to determine whether each ticket cost $26 or $28 so i didn't get this question so yeahyou have a good day.