Greetings!
When trying to find the percentage, simply use this equation:
(Initial price x [tex]\frac{percentage}{100}[/tex])
Where the initial price is the total amount, and the percentage is how much the percentage is. Simply plug the numbers in the question into this equation:
(380 x ([tex]\frac{5}{100}[/tex])
= 380 x 0.05 = 19
So 5% of $380 = 19
As 15% is simply 3 times more than 5:
15 ÷ 5 = 3
You can simply multiply 19 by 3 to find 15%!
19 x 3 = 57
So 15% of $380 = $57
Hope this helps!