Answer:
En 1953 determinó con exactitud la edad de la Tierra en 4.550 millones de años, con un margen de error de unos 70 millones de años.
Explanation:
The main reason for the wall's construction had always been defense. Since China's first dynasty, the empire faced a near-constant threat of attack from the nomadic tribes to the north. This included those famed Mongols as well as lesser-known groups like the Xiongnu and the Göktürks.
Precious gems would be my best guess, it's the only natural rescource that's only in one area. Sooo.... Precious gems i guess
Average x = (5-1)/2 = 2
<span>average y = (-2+3)/2 = 1/2
</span>so
<span>(2 , 1/2)</span><span>
</span>
