Answer:
Slope = 
Step-by-step explanation:
Slope of a straight line passing two points
and
is given by the formula,
m = 
From the graph attached,
Line is passing through two points (20, 5) and (80, 20),
Therefore, slope of the line will be,
m = 
m = 
The slope is
.
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Answer:

___________________
Step-by-step explanation:
Look at the photo below for the details.
:)
Answer:
30
Step-by-step explanation:
So we begin by assigning variables to each side with:
DE = x
EF = y
DF = z
Now we start listing a system of equations from what is given:
x+y+z=81
x=2y
x-4=z
Once we solve that with substitution, we get the result of:
x=34
y=17
z=30.
Since z is the length of DF, the length of DF is 30.
I hope this helped! :D
Answer: The prime numbers are 1, 2, 3, 5, 7.