Answer:
The answer is x = 9
We use Pythagoras theorem to form the equation and solve for x
That's
a² = b² + c²
where a is the hypotenuse
we get
(x + 6)² = 12² + x²
Expand
x² + 12x + 36 = 144 + x²
Group like terms
We have
x² - x ² + 12x = 144 - 36
12x = 108
Divide both sides by 9
That's
12x/12 = 108/12
x = 9
Hope this helps you.