Suppose the profit rate at the beginning of the month is x,

because

Selling price = purchase price (1+ profit)

Price at the beginning of the month = original purchase price *( 1+x)

After the purchase price is reduced at the end of the month, it is

Price =( 1+ 10%+x)* original purchase price *( 1-8%)

Because the sales price remains unchanged.

, yes

( 1+ 10%+x)*( 1-8%)=( 1+x)

( 1. 1+x)* 0.92 = 1+x

1.0 12+0.92 x = 1+x

0.08x=0.0 12

x=0. 15

That is, the profit margin at the beginning of the month is 15%.