Which natural number fits the position of [[$ x $]] ?

a) [[$ x^2 + 19^2 = 386 $]]



Answer: The number is [[$ x = $]] .

b) [[$ 15^2 + x^2 = 17^2 $]]



Answer: The number is [[$ x = $]] .

c) [[$ 12^2 + 5^2 = x^2 $]]



Answer: The number is [[$ x = $]] .

d) [[$ 30^2 + x^2 = 1341 $]]



Answer: The number is [[$ x = $]] .