If you times 39.99 by 0.20 (20%) then you get your answer of $7.99
To find the answers, substitute the variables (letters) in the equation for the number on that line that corresponds to that letter, then solve with the equation.
Answer:
The correct option is D.
Step-by-step explanation:
The given expression is

Difference of two squares property:

Using the above property, the given expression can be written as

Applying square we get


Therefore the correct option is D.
The answer to b is 24×600=14400
24=hours in a day
600=blooded pumped per hour
14400=the amount the blood is pumped a day