Viết ra giá trị đầu và giá trị cuối. Xác định mức độ tăng. Lấy đáp án chia cho giá trị đầu. Nhân kết quả với 100.

Given the above summary, write a detailed text in English for it.
For example, let's say your auto insurance premium just went up. Write down these values:  Your car insurance premium was $400 before the increase. This is the starting value. After the increase, it costs $450. This is the end value. Subtract the starting value from the end value to find the out how much it increased. We're still working with ordinary numbers at this point, not percentages. In our example, $450 - $400 = a $50 increase. A percentage is just a special kind of fraction. For example, "5% of doctors" is quick way to write "5 out of 100 doctors." By dividing the answer by the starting value, we turn it into a fraction that compares the two values. In our example, $50 / $400 = 0.125. This converts your last result into a percentage. The final answer to our example is 0.125 x 100 = 12.5% increase in auto insurance premiums.