Hey there :)
To find the slope with <em>two points</em> we will need to use the equation 

( 3 , -20 ) ( 5 , 8 )
Here is what the equation should look like when replaced with the numbers (<em>it will be a fraction</em>) :

We know that <em>two negatives</em> cancel out and make a positive, so the numerator would actually be 8 + 20.
Solve the fraction and we get 
28 <em>divided</em> by 2 is 14. The slope is 14.
Answer:
<u>The correct answer is that the area of the regular octagon is 309 cm²</u>
Step-by-step explanation:
There are several formulas for calculating the area of a regular octagon. We will use this one for solving this question because it does not require additional information .
Area = (2 * s²)/tan 22,5°
s = 8 cm
Replacing with the real values, we have:
Area = (2 * 8²)/tan 22,5°
Area = 2 * 64/0.4142
Area = 128/0.4142
<u>Area = 309 cm² (Rounding to the nearest tenth)</u>
A could be 2 while B could be 3, so -2a+3b turns into -4+9, which equals 5.
From what I know you can't really solve a a single equation with two-variables so it's just a matter of trial and error.
Just try plugging in a small number like 2 for a just to try it and you get 8b^2=72.
Divide everything by 8 to isolate b and you get that b^2=9.
Square root everything and you'll find that b=3. This is just one possible combination, I'm sure there are many more but this is obviously the one that was intended to be found.
Now that we know that a=2 and b=3 just plug them into the equation.
-2(2)+3(3)=?
-4+9=?
5
Sorry about having to use this ^ symbol, the equation maker is not working.