Answer:
....coefficients are calculated
30% discount = 1-(30/100)= 0.7
10% reduction = 1-(10/100) = 0.9
10% reduction =1-(10/100)=0.90
overall evolution coefficient: 0.7*0.9*.09=0.567
percentage of initial cost of winter sweaters, excluding sales tax: (0.567-1)*100=-43.3%.
% decrease = 43.3%