Question 268094
Let x=amount of money saved by the sisters
Oldest sister took (1/2)x-1 dollars, leaving x-((1/2)x-1) or (1/2)x+1
second oldest sister took (1/2){(1/2)x+1)}+1 or(1/4)x+1/2+1 which 
equals (1/4)x+3/2, thus leaving (1/2)x+1-{(1/4)x+3/2} and this equals
(1/2)x+1-(1/4)x-3/2 or (1/4)x-1/2 and we are told that this totals $8, so
(1/4)x-1/2=8  multiply each term by 4
x-2=32 add 2 to each side
x=$34----amount of money saved by the sisters

CK
Oldest sister took (1/2)*34-1=17-1=16 leaving 18
Second oldest sister took(1/2)*18+1=9+1=10 leaving 18-10=$8 for the youngest sis

Does this help?---ptaylor