Positive becaus Mexico city is right
To change the equation, you'd have to take the square root of both sides. When you do this, x^2 cancels out leaving you with x = sqrt(y)
If you need help on the other ones, all you have to do is solve for x by using either addition/subtraction or dividing/multiplying.
The freshet is basically a flood that occurs because of heavy rainfall or because of the melting of a snow.
This type of flooding is most common in the valleys of the larger rivers, especially the ones that start their flow high in the mountains.
The large rivers have much more water, and they also have lot of tributaries, so when there's a heavy rainfall they receive enormous amounts of water, which easily causes a flood.
Also, when the snow melts, lot of water is released from it, and most of that water gets into the river, or first in its tributaries and that in it, so there's a high possibility of a big flood occurring suddenly.
Magma. Magma can be made of many different materials, and once it breaches the earth surface it is called lava. Lava is what comes out of volcanoes, magma is what is still underground
Two ways in which the proximity to water has affected Western Europe's economy:
1) Proximity of water can lead to lack of food, which affects economy of the country in various ways.
2) It has wet cool summers and wet, mild winters, so for shelters and cloths, it affects economy by transportation, extra manufacture etc.
Hope this helps!