किसी संख्या का 20%, 620 के 20% से 200 अधिक है। वह संख्या क्या है?

A person saves 90% of his income. If his expenditure is ₹520, find his income (in ₹).

By how much is 30% of 60 greater than 25% of 40?

By how much is 30% of 50 greater than 35% of 30?