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:
y=-1
Step-by-step explanation:
it is a straight line graph with no gradient therefore no X value. It crosses the y axis at -1
Answer:
The median-median line is a better prediction.
Step-by-step explanation:
Both lines predict a value for x=50 that is less than 60. The median-median line value is closer to 60, so could be considered a better prediction.
X^2 + 8x + 7 = 0
x^2 + 7x + x + 7 = 0
x(x + 7) + 1(x + 7) = 0
(x + 7) (x + 1) = 0
x = -7 or x = -1