Answer:
Option C is correct
$120
Step-by-step explanation:
The equation of best line is given by:
....[1]
where, y represents the total amount of money earned in tip after x hours, m is the slope and b is the y-intercept.
As per the statement:
From the graph:
Two points are:
(2, 20) and (8, 80)
Formula for slope(m) is given by:
![m = \frac{y_2-y_1}{x_2-x_1}](https://tex.z-dn.net/?f=m%20%3D%20%5Cfrac%7By_2-y_1%7D%7Bx_2-x_1%7D)
then;
![m = \frac{80-20}{8-2}=\frac{60}{6}=10](https://tex.z-dn.net/?f=m%20%3D%20%5Cfrac%7B80-20%7D%7B8-2%7D%3D%5Cfrac%7B60%7D%7B6%7D%3D10)
⇒m = 10
Substitute in [1] we have;
![y = 10x+b](https://tex.z-dn.net/?f=y%20%3D%2010x%2Bb)
Also , substitute the point (2, 20) to find b;
![20= 10(2)+b](https://tex.z-dn.net/?f=20%3D%2010%282%29%2Bb)
⇒![20=20+b](https://tex.z-dn.net/?f=20%3D20%2Bb)
Subtract 20 from both sides we have;
⇒0 = b
or
b = 0
Then, we get the equation:
![y=10x](https://tex.z-dn.net/?f=y%3D10x)
We have to find total amount of money earned in tips after working 12 hours.
⇒x = 12 hours
then;
![y=10(12) =120](https://tex.z-dn.net/?f=y%3D10%2812%29%20%3D120)
Therefore, the total amount of money earned in tips after working 12 hours is, $120