What does the red plus mean?

What created the number system based on 6? What percent of 8760 hours is 13 hours? What is the word for something done on purpose? What is 9 didvided by 3? What is the circumference and radius of a circle if it 14cm? What material allows electrical energy to move through it? How long is 60000 seconds? What is polynomial nomenclature? How do you graph the relationship between the amount of gas to how far you can travel? Why 57 51 are not prime numbers? Which shape line of symmetry but no rotational symmetry? What is the least common multiple of 8 and 8? What is a metaphor for a complex fraction? The number of beats in poetry is called? How much liguid volume is 850 cc's? What are four consecutive numbers that add up to -14? How many units in 1 acre? What comes next in this pattern 6 10 8 12 10 14 12 16 14? What is the answer for 2 radical 54? What are the 3 common fractions?