In August, Xavier gave his wife, Lynn, $8000 for household expenditure. Lynn spent 50% of the sum on rental, 20% on food and saved the rest. In September, Xavier reduced the sum he gave to Lynn. Lynn 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 September. By what percentage was the sum given to Lynn reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$8000
Change		- 2%	- ?	- ?
After	50%	18%
Comparing the amounts spent in September	80 u		20 u	100 u

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

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

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

100% → 8000

1% → 8000 ÷ 100 = 80

68% → 68 x  80 = 5440

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

80 u = 68% 

80 u = 5440

1 u = 5440 ÷ 80 = 68

Amount that Xavier gave to Lynn in September
= 100 u
= 100 x 68
= $6800

Amount that Lynn received less from Xavier from August to September
= 8000 - 6800
= $1200

Percentage that the sum given to Lynn was reduced by from August to September
= ¹²⁰⁰₈₀₀₀ x 100%
= 15%

Answer(s): 15%