To answer this item, we let x be the number that is not unknown in this item such that the situation in this problem can be expressed as follows,
x - 9.3 = 68.91
Adding 9.3 to both sides of the equation,
x - 9.3 + 9.3 = 68.91 + 9.3
Simplifying,
x = 78.21
The answer to this item is 78.21, this I think is the first choice except that it is mistakenly written as 7.21 only.
Indian, Pacific, Atlantic, Arctic Oceans are the 4
Tectonic plates are parts (pieces) of the outermost layer of Earth: the Crust. (the outermost part of the mantle is also often included in the plates). This means that the land in the middle of the plates is relatively stable while the borders of the plates can be in movement - after all this is where two pieces meet. Plate borders are where the vocanoes and Earthquakes often take place.
C. Australia is moving at about ~7 centimeters a year, which is about 67 millimeters.