Answer:
27
Step-by-step explanation:
First you need to find x.
It is shown that DE=EF, so we can use this.
5x-3=3x+7
5x=3x+10
2x=10
x=5
Then, you plug in the value of the variable and solve.
6(5)-3
30-3
27 = DF
Answer: (13,-7)
Step-by-step explanation:
By using the formula 
is the coordinates of the midpoint.
For finding the midpoint X variable do:

For finding the midpoint Y variable do:
(you can either keep the parenthesis or take them out. Either way, the answer is the same.
Considering coordinate numbers follow the format: (x,y), you'll simply just substitute the numbers found above into their respective places.
x: 13
y: -7
(13,-7).
Answer: (-2 -9)
Step-by-step explanation:
Have no time