The tie original price is $35. First, we need to calculate the discount over this price. To find 40% of a quantity, we just multiply the quantity by 40 and divide by 100.

The discount is equal to $14. To find the price of the tie with the discount, we subtract the discount value from the original price.

The tax is 8%, calculating the tax of the discounted price, we have

Adding the tax to the price, we have

Now, we subtract the $15 their mother gave them to help from the price

They paid together $7.68, since the girls will split the cost evenly, to find the value each paid we just need to divide this amount by 2.

Each sister paid $3.84.