Answer: x=35
Explanation:
To find the value of x, we can use the Pythegorean Theorem because this is a right triangle.
Pythagorean Theorem: a²+b²=c²
 [exponent and distribute]
 [exponent and distribute]
 [subtract both sides by 144]
 [subtract both sides by 144]
 [subtract both sides by x²+4x]
 [subtract both sides by x²+4x]
 [divide both sides by -4]
 [divide both sides by -4]

Now, we know that x=35.