Answer:
C. 
General Formulas and Concepts:
<u>Calculus</u>
- Mean Value Theorem (MVT) - If f is continuous on interval [a, b], then there is a c∈[a, b] such that

- MVT is also Average Value
Step-by-step explanation:
<u>Step 1: Define</u>

f'(c) = 20
Interval [1, b]
<u>Step 2: Check/Identify</u>
Function [1, b] is continuous.
Derivative [1, b] is continuous.
∴ There exists a c∈[1, b] such that 
<u>Step 3: Mean Value Theorem</u>
- Substitute:

- Rewrite:

And we have our final answer!
Answer:
sine 23 = x/21
Multiply both sides by 21
21 x sine 23 = x
Now, use a calculator and find the answer of the 21 times the sine of 23:
x = -17.7706284876
My answer was wrong, please delete this
<span>This one is the correct answer----->Multiply the bottom equation by 2 thus eliminating the y variable when the equations are added together.
</span><span>X + 6y = 2 ....top
</span><span>4x - 3y = 10...bottom
if we multiply the bottom equation by 2 .......... => 8x - 6y = 20
if we add it to the top one..........>(8+1)x +(6-6)y = (20+2)
then we solve for x => x = 22/9
then with the top equation, we solve for y == > y = -2/27</span>