Answer:
(C)Determine the principal square root of both sides of the equation.
Step-by-step explanation:
Given: Isosceles right triangle XYZ (45°–45°–90° triangle)
To Prove: In a 45°–45°–90° triangle, the hypotenuse is
times the length of each leg.
Proof:

Because triangle XYZ is a right triangle, the side lengths must satisfy the Pythagorean theorem, 
Since a=b in an isosceles triangle:

Therefore, the next step is to Determine the principal square root of both sides of the equation.
Devin borrowed $1,058 at 13 percent for nine months.
We have to calculate the interest paid.
Interest = 
Substituting the values of
Principal = $1058
Rate = 13%
Time = 9 months =
year
Interest = 
Interest = 103.155
= 103.16
So, Devin will pay 103.16 as the interest.
Therefore, Option A is the correct answer.
m□ebd=4 x-8 and m□ebc=5 x+20
This is solvable only if e b is the initial side and b d and b c lies on opposite side of each other and lies on a line i.e c,b,d are Collinear.
∠ebd and ∠ebc will form a linear pair.The meaning of linear pair is that angles forming on one side of a straight line through a common vertex which are adjacent is 180°.
i.e
∠ ebd + ∠ebc = 180°
4 x- 8 + 5x + 20= 180°
adding like terms
⇒ 9 x +12 =180°
⇒ 9 x = 180° - 12
⇒ 9 x = 168°
⇒ x =( 168/9)°=(56/3)°
now m□ebc =5 x +20
= 5 × 56/3 + 20
= 280/3 + 20
=340/3
m□ebc=( 340/3)°
So, solution set is x =(56/3)° and m□ebc =(340/3)°