You use the Pythagorean theorem which is a^2+b^2=c^2
So....
.8^2+.6^2=c^2
.64+.36=c^2
1=c^2
1=c becaaue the square root of one is one
The correct answer is three.
Answer:

Step-by-step explanation:
Given points are 
And given transformation is

We will start from left to right.
First transformation is reflection about x-axis.
When we reflect about x-axis 
So, ![(-1,-8)=[-1,-(-8)]=(-1,8)](https://tex.z-dn.net/?f=%28-1%2C-8%29%3D%5B-1%2C-%28-8%29%5D%3D%28-1%2C8%29)
Now next transformation is dilation with a factor 4.
If we do dilation with a factor
to the point 
New co-ordinates after dilation became 
So, 
5x + -4y = 13
Solving
-5x + -4y = 13
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '4y' to each side of the equation.
-5x + -4y + 4y = 13 + 4y
Combine like terms: -4y + 4y = 0
-5x + 0 = 13 + 4y
-5x = 13 + 4y
Divide each side by '-5'.
x = -2.6 + -0.8y
Simplifying
x = -2.6 + -0.8y
Simplifying
3x + -4y + -11 = 0
Reorder the terms:
-11 + 3x + -4y = 0
Solving
-11 + 3x + -4y = 0
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '11' to each side of the equation.
-11 + 3x + 11 + -4y = 0 + 11
Reorder the terms:
-11 + 11 + 3x + -4y = 0 + 11
Combine like terms: -11 + 11 = 0
0 + 3x + -4y = 0 + 11
3x + -4y = 0 + 11Combine like terms: 0 + 11 = 11
3x + -4y = 11
Add '4y' to each side of the equation.
3x + -4y + 4y = 11 + 4y
Combine like terms: -4y + 4y = 0
3x + 0 = 11 + 4y
3x = 11 + 4y
Divide each side by '3'.
x = 3.666666667 + 1.333333333y
Simplifying
x = 3.666666667 + 1.333333333y