maths.....form 1

1)Jacky plans to buy a pair of shoes.Two weeks ago,he saved 40%of the sellig price of the shoes.Last week,he saved 80% of the rest.This week,the shoes are on sale at a 10% discount,but he still owes $12.Find the original selling price of the shoes.
Let the original selling price of the shoes be $x.
Two weeks ago the amount he saved
= $x (40%)
= $0.4x
One week ago the amount he saved
= $x (1-40%)(80%)
= $x (0.6)(0.8)
= $0.48x
The selling price at discount
= $x (1-10%)
= $0.9x
So $0.4x + $0.48x + $12 = $0.9x
0.4x + 0.48x + 12 = 0.9x
0.88x + 12 = 0.9x
0.02x = 12
x = 600
So the original selling price of the shoes is $600.

y=price of shoes

yx90%-yx40%-yx(1-40%)x80%=$12

ans=$600

$600

Y = price of shoes

Y x 90% - Y x 40% - Y x 60% x 80% = $12