The population of a city is 45,000 and decreases 2% each year. if the trend continues, what will the population be after 15 years

The answer is 31,500.
Let's clarify some things :
1% of 45,000 is 450
Maybe you're wondering why , it's actually very simple .
Just move the decimal to the left once if you want to find 10% , move the decimal twice if you want to find 1%.
We now that 1% equals 450. Then 2% equals to
Well just add another 1% .
450 + 450 or 450 times 2
Which equals 900.
Now we want to find what's the population after 15 years.
900 times 15= 13,500
But that's not the answer
That's what is decreasing.
45,000 - 13,500= 31,500
That's why the answer is 31,500.