Answer: 6.5
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Step-by-step explanation:
This is a visual example of the pythagorean theorem. We add the areas of the two squares to get
13+29.25 = 42.25
Then we apply the square root to this to get the value of x, which is the hypotenuse of the right triangle
x = sqrt(42.25) = 6.5
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Side note: if you're curious about finding the other lengths of the triangle, apply the square root to those areas. The blue area 29.25 will lead to a side length of approximately sqrt(29.25) = 5.4083269; the red square will follow the same idea.