Answer:
A biconditional statement is a combination of a conditional statement Its converse written in the if and only form
Answer for the question is A
A stuntman jumping off a 20-m-high building is modeled by the equation h = 20 – 5t2, where t is the time in seconds. A high-speed camera is ready to film him between 15 m and 10 m above the ground. For which interval of time should the camera film him?
Answer:

Step-by-step explanation:
Given:
A stuntman jumping off a 20-m-high building is modeled by the equation
-----------(1)
A high-speed camera is ready to making film between 15 m and 10 m above the ground
when the stuntman is 15m above the ground.
height
Put height value in equation 1





We know that the time is always positive, therefore 
when the stuntman is 10m above the ground.
height
Put height value in equation 1







Therefore ,time interval of camera film him is 
Answer:
2 : 5
Step-by-step explanation:
Ratio expresses the relationship between two or more numbers. It shows the frequency of the number of times that one value is contained within other value(s).
We are to determine the ratio of dimes to nickels
total sum of nickels = 3 + 12 = 15
total sum of dimes = 4 + 2 = 6
6 : 15
three can divide each of the numbers
2 : 5