Well, the first 16 were about 16*75=$1200 extra. The last 8 were $720 lost. Thus, the total profit is $480. He bought them with $7200, which means the profit is around 6.67%.

$=(a^2-10a)-(b^2+6b) +16$
$=[(a^2-2(5)a+25)-25]-[(b^2+2(3)b+9)-9]+16$
$=(a-5)^2-25-(b+3)^2+9+16$
$=(a-5)^2-(b+3)^2$
You multiply 18 by 8 and you get 144
so the puppys weight is 144oz now