Answer:

Step-by-step explanation:
Given:

We need to complete this Statement.
By Solving the above equation we get;
We will take some common factor out so we will get;

Hence the Complete statement is 
Focus on triangles DFC and DFE:
- They are both right triangles because DF is perpendicular to EC
- DC=DE
- DF is a common side
So, the two triangles are congruent. It follows that CF=FE, and in particular

And since x=3, the length of EF is

You would need to use the distance formula.
Distance = Sqrt((x2-x1)^2+(y2-y1)^2)
Plug in your numbers
Distance = Sqrt((12+4)^2+(12-18)^2)
Distance = 17.09
Move the -3 to the other side which makes it 41 + 3 = 44
So now the equation looks like 4x=44
Now divide 44 by 4, equals 11
x=11