If you would like to know how much profit on each share did he make, you can calculate this using the following steps:
$12,000 / $8 = 1,500 shares
$15,000 / 1,500 shares = $10 per share
x% of $8 is $10
x/100 * 8 = 10 /*100/8
x = 10 * 100 / 8
x = 125%
125% - 100% = 25%
Miguel made 25% ($2) profit on each share.
