Answer:
x ≈ 3.9
Explanation:
Call the segment shared by the two triangle "y". The Pythagorean theorem tells you ...
sum of squares of sides = square of hypotenuse
y² +6² = 10²
x² +7² = y²
Substituting for y² using the second equation, we get ...
x² +7² +6² = 10²
x² = 10² -7² -6² = 100 -49 -36 = 15
Taking the square root, we find ...
x = √15 ≈ 3.9