Answer:
He made $12 by selling the bicycle helmet to Jin!
Explanation:
Let x be the original cost of the bicycle.
The cost of the helmet is $16, so the original cost of the bicycle and helmet is x + $16 algebraically.
Jin pays a total of $116 + $16 = $132 for the bicycle and helmet, which is 120% of what Stefan spent originally, so x + $16 = 1.2 * (x + $16)
Expanding the right-hand side gives x + $16 = 1.2x + 1.2 * $16.
Solving for x, we find that x = $104.
So, Stefan originally spent $104 for the bicycle and $16 for the helmet, for a total of $104 + $16 = $120.
Stefan sells the bicycle and helmet to Jin for $116 + $16 = $132, so he makes a profit of $132 - $120 = $12.