Why did the mayan civilization come to an end?

The Maya for really inexplicable reasons collapsed as a civilization. This is called the mayan mystery and this references the collapse of the civilizations and the fact that we don't know why. We have yet to figure out a clear reason why the Maya ceased to exist at the civilization. We know what happened to the Aztecs, they were destroyed by the Spanish. In the same way, the Inca were destroyed by the Spanish. We know what happened to Rome, we know what happened to Greece, we know what happened to the Han. We know what happened to all of these civilizations but for the Maya, we just don't know and it drives scientists and historians nuts.

The Maya had reached such colossal civilization heights. They're accomplishments are undeniable and outstanding and unusual and what is crazy is that the collapse is so quick. Normally you see a gradual decline of an empire and then it crumbles and fades away. Very rarely do empires just disappear very quickly without really an explanation. Now, dozens and dozens and dozens and dozens of Mayan cities have been excavated and we know a ton of information about that Maya. We know what they look like, how they worship, how they ate, ruling family lineages, deciphered Mayan writing, we can read Mayan texts and all that information does not lead us any closer to figuring out what happened to them. There is just no smoking gun and no solid evidence.

The problem is not much written record survives because the Maya were gone around 500 years before the Spanish even got here so when the Spanish got here, the Mayan civilization was already gone. The written records that were around like the books were destroyed by the Spanish.

The Spanish destroyed the books because they were saw the Mayans as  corrupted and they wanted to give them Christ and save them and part of that was destroying all remnants of their culture.

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69