It is used to see if a graph represents a function because if there is 2 dots or intersecting lines within the other lines then it is not a function. if there is only one line or dot, then yes, it is a function. hope i explained it well.
Answer:

Step-by-step explanation:

Answer:
z = 1/4
Step-by-step explanation:
See attached image
I got you bro the answer is c
Answer:
40 problems in 100 minutes
Step-by-step explanation:
This is a ratio problem.
You first divide 30 minutes by three to get how many problems she can do in 10 minutes. What you do to one side you do to the other side. So then, you should have 4 problems in 10 minute. Then, you multiply 10 by 10 and 4 by 10 to get 40 problems in 100 minutes.