How to solve problems with positive and negative numbers​

In the final round of trivia competition, contestants were asked to name as many states that begin with the letter m as they could in 15 seconds. the bar graph shows the number of states the contestants were able to name. how many contestants participated in the final round of the competition?

What is the approximate circumference of the circle shown below?

Empty box + box + empty box fill in the box is equal to 30 how