Here, we want to get the value of x
As we can see, we have the interior angle as 45;
The other is 90; and that means the last angle will be 45
This mean that we have an isosceles right-triangle
The sides that face the angles are equal
These sides are x and 12
That means x = 12
To get the value of y, we have to use the Pythagoras' theorem
The square of the hypotenuse (the longest side and the side that faces the right angle) is equal to the sum of the squares of the two other sides
The side facing the right angle is y
So, the sum of the squares of x and 12 will give the square of y
Mathematically, we have this as follows;
[tex]\begin{gathered} y^2=12^2+x^2 \\ \sin ce\text{ x = 12} \\ y^2=12^2+12^2 \\ y^2\text{ = 144 + 144} \\ y^2\text{ = 288} \\ y\text{ = }\sqrt[]{288} \\ y\text{ = 12}\sqrt[]{\text{ 2}} \end{gathered}[/tex]