From the given information, a exists jointly proportional to b and c.
then 
Therefore, the value of a exists 2.
<h3>
What is the value of a?</h3>
Given, a exists jointly proportional to b and c.

Taking K as the constant of proportionality.
a = K b c
For b = 8 and c = 9, the value of a = 4
4 = K(8)(9)
4 = 72 K
Dividing the equation by 72, we get

Using the value of K in the equation:

Substitute the values of b = 2 and c = 18, in the above equation

a = 2
Therefore, the value of a exists 2.
To learn more the value of x refers to:
brainly.com/question/11874663
#SPJ4
The mean is the average of the numbers: a calculated "central" value of a set of numbers.
Therefore: If the amount spent on books per month by all her classmates is leveled that amount would be $30
To calculate it: add up all the numbers, then divide by how many numbers there are
Answer: 
Step-by-step explanation:

Answer:
C ) 40w + 300 > 7--
Step-by-step explanation:
Since he starts off with 300 cards, the equation must have +300 units. As he purchases 40 each week, the rate of change is 40w. Since his goal is over 700, look for >700.
Therefore 40w + 300 > 700
First find the length of the side by taking the square root of 112.
There are 4 sides so multiply your answer by 4 to get the perimeter.
The answer is 42.332 which rounds to 42.