Yes it is.
Step by step explanation:
the picture in the attached figure
we know that
if ABC is an isosceles triangle
then
AB=BC
angle A=angle C=45 degrees
and
triangle ABD and triangle BDC also are isosceles triangles
AD=BD=x
DC=BD=x
the hypotenuse AC is equal to

To find the length AB applying the Pythagorean Theorem

remember that AB=BC


therefore
the answer is
the length of one leg of the large right triangle in terms of x is equal to 
10x+12/2. Add the x's and the normal numbers and put the equation over 2
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We have the perimeter of first dimension 2(8 + 4) = 24;
The perimeter of the second dimension is 2( 8 + 54 + 4 + 54 ) = 240
We calculate p/100 = 24/240;
Then p/100 = 1/10;
p = 100/10;
p = 10;
Finally, 10% is the answer.