Explain how you can use the number line to find the sum

Is the following relation a function? x y 1 4 −1 −2 3 10 5 16 yes no

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?