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
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Answer: a
Step-by-step explanation:
none of the answers in b are divisible by 4
Any quadrilateral has sum of all angles equal 360⁰.
So,
m∠D+78+91+90=360
m∠D=360-(78+91+90)=101⁰
Answer is A.
Short Answer B
Remark
You need not do any calculations to get the answer. You are required just to read the graph. Doing the calculations would be beneficial but unnecessary.
Step One
Find the x value.
1. If you have a ruler or a straight edge of some kind, put it on the cross point of the two graphs.
2. Make the ruler go straight up and down. You will find out it goes 1 point back of the 5.
3. Count the number of squares from 0,0 or when y = 0.
4. You will find you have to count 4 squares along the x axis.
The x value is 4.
Step Two
1. Put the ruler on the cross point again. This time make it go straight across.
2. Count up from (0,0)
You should get 8.
The y value is 8
Answer: (4,8)