This process is known as thermohaline circulation. In the Earth's polar regions ocean water gets very cold, forming sea ice. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink.
Angles in a triangle add up to 180 degrees.
180 - 125 = 55
Add the ratios 4+7 = 11
Divide the left over angels by the ratio: 55/11 = 5
Now multiply 5 by each side of the ratio:
4:7
4*5 = 20
7*5 = 35
So the 2 angles are 20 and 35 degrees.
To check, you can add up all the angels : 20 + 35 + 125 = 180
So we know 20 and 35 is correct because it adds up to 180 degrees :)