In November, Reggie gave his wife, Gem, $6000 for household expenditure. Gem spent 50% of the sum on rental, 20% on food and saved the rest. In December, Reggie reduced the sum he gave to Gem. Gem spent the same amount on rental and reduced the amount she spent on food by 10%. She saved the remaining 20% of the sum given to her in December. By what percentage was the sum given to Gem reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$6000
Change		- 2%	- ?	- ?
After	50%	18%
Comparing the amounts spent in December	80 u		20 u	100 u

Amount that Reggie saved in percent
= 100% - 50% - 20%
= 30%

Amount that Reggie reduced on food in percent
= 10% x 20%
= ¹⁰₁₀₀ x 20
= 2%

Total amount that Reggie spent on rental and food in percent
= 50% + 18%
= 68%

100% → 6000

1% → 6000 ÷ 100 = 60

68% → 68 x  60 = 4080

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

80 u = 68% 

80 u = 4080

1 u = 4080 ÷ 80 = 51

Amount that Reggie gave to Gem in December
= 100 u
= 100 x 51
= $5100

Amount that Gem received less from Reggie from November to December
= 6000 - 5100
= $900

Percentage that the sum given to Gem was reduced by from November to December
= ⁹⁰⁰₆₀₀₀ x 100%
= 15%

Answer(s): 15%