Answer :
Yes your method is correct. But you will need to express it in percentage in the end.
So,
2 x 12 ( dozen ) = 24
24 - 18 = 6
6 / 12 = 0.5
$6 is how much you earned by selling 12 hair products.
Hence, $0.50 is how much you earned per bottle.
Transfering 0.5 into percentage would be 0.5 x 100.
Your percentage mark up would be 50 %
So,
2 x 12 ( dozen ) = 24
24 - 18 = 6
6 / 12 = 0.5
$6 is how much you earned by selling 12 hair products.
Hence, $0.50 is how much you earned per bottle.
Transfering 0.5 into percentage would be 0.5 x 100.
Your percentage mark up would be 50 %
2*12=24
24-18=6
6 for price of 12 hair products sold
6/12=.5
.5 for percentage
50% mark up
24-18=6
6 for price of 12 hair products sold
6/12=.5
.5 for percentage
50% mark up