I see that you're on the right path, with subtracting 180 from 207.
You know the difference is 27, you have to divide 27 by 180, since 180 was the initial price.
27/180=.15; Now you want to multiply .15 by 100 so you can get a percentage.
.15×100= 15
So it increased by 15%.
Tell me if this helped!! I can exlplain it more if it's needed.