In November, Sean gave his wife, Xuan, $9000 for household expenditure. Xuan spent 60% of the sum on rental, 30% on food and saved the rest. In December, Sean reduced the sum he gave to Xuan. Xuan spent the same amount on rental and reduced the amount she spent on food by 30%. She saved the remaining 10% of the sum given to her in December. By what percentage was the sum given to Xuan reduced by?

	Rental	Food	Savings	Total
Before	60%	30%	10%	$9000
Change		- 9%	- ?	- ?
After	60%	21%
Comparing the amounts spent in December	90 u		10 u	100 u

Amount that Sean saved in percent
= 100% - 60% - 30%
= 10%

Amount that Sean reduced on food in percent
= 30% x 30%
= ³⁰₁₀₀ x 30
= 9%

Total amount that Sean spent on rental and food in percent
= 60% + 21%
= 81%

100% → 9000

1% → 9000 ÷ 100 = 90

81% → 81 x  90 = 7290

The total amount that Sean spent on rental and food is repeated. 

90 u = 81% 

90 u = 7290

1 u = 7290 ÷ 90 = 81

Amount that Sean gave to Xuan in December
= 100 u
= 100 x 81
= $8100

Amount that Xuan received less from Sean from November to December
= 9000 - 8100
= $900

Percentage that the sum given to Xuan was reduced by from November to December
= ⁹⁰⁰₉₀₀₀ x 100%
= 10%

Answer(s): 10%