Non-calculator
Method
You divide both sides by 10 to get 10%
You divide by 10 to get 1%
Now you divide by 2 to get 0.5 (or 1/2 of 1)
You can find 2% by multiplying 2 to 1% and 2
Now you need to add the 10% with 0.5% and 2% which give you 12.5%.
Now you takeaway 25 from 200
Decrease 200 by 12.5%