Help me out with these questions please? 5+ 3x = 8 and also 3x - 6 =9

Fredrick designed an experiment in which he spun a spinner 20 times and recorded the results of each spin

The sum of five and a number n is at least 12

Arace is 10 kilometers long. markers will be placed at the beginning and end of the race course and at each 500 meter mark. how many markers are needed to mark the course for the race?