The number of right-handed students in a math class is nine times the number of left-handed students. the total number of students in the class is 30. how many left-handed students are in the class?

R - Right Handed 
L - Left Handed 

R = 9L ( the number of right handed kids is equal to having 9*number of left handed kids) 
9L + L = 30  ( since total number of people in class is 30) 
10L = 30 
( Divide by 10 both sides )
L = 3 

so... There are 3 Left Handed kids and 27 Right Handed kids ( since R = 9L , R = 9(3) = 27)

Hope this helped!

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.