We have two triangles with the same angles, then, they're are proportional to each other.
By the pythagorean theorem we can find the missing side of the smallest triangle:
pythagorean theorem:
Where 'c' represents the hypotenuse, and 'a' and 'b' represent the other two sides. Applying this theorem in the smallest triangle we have the following relation:
Now that we have our missing side, we can compare the smallest triangle with the biggest triangle.
The ration between 4 and 8 is the same of the hypotenuses of both triangles( x and 5)
Then, we have the following equation:
Just solving this equation, we get the following result