Algebra is number 3 - You have subtracted the measure of angle HKI from the equation.
Transitive property of equality is number 2 - Because both pairs of angles equal 180 degrees, you can set them equal to each other.
Definition of congruence is number 4 - The congruence symbol is in the equation, which tells you that the two angles are congruent.
Angles forming a linear pair sum to 180 degrees is number 1 - 180 degrees is in the equations given and the angles all form linear pairs.
Hope this helps!! :)
Answer:

Step-by-step explanation:

Simplify to get 
Find what
equals to by taking away 8,
.
Divide by 2 to find x, 
Answer:
x=-1/3, y=-13/3. (-1/3, -13/3).
Step-by-step explanation:
y=x-4
4x-y=3
------------
4x-(x-4)=3
4x-x+4=3
3x+4=3
3x=3-4
3x=-1
x=-1/3
y=-1/3-4
y=-1/3-12/3=-13/3
The new square has length: 10 + l, where l is the original length of the square, and it's area is (10 + l)^2;
So, we solve the equation: 3 x l^2 = (10 + l)^2;
Then, 3 x l^2 = 100 + 20 x l + l^2;
Finally, 2xl^2 - 20xl - 100 = 0; / ÷2;
l^2 - 10l - 50 = 0 (we use the quadratic equation formula);
The only positive solution is l = 5(1+ \sqrt{3} );
The answer will be 20. 16=80%. 1=0.2%.100%=20