Hi, I'm revising for my gcse exam in June and struggling with these two topics.

Percentage Decrease: What is the new cost after a price of £56 is decreased by 15%? Work it out as 0.85 *5g=£47.50 This is a question from a GCSE revision guide, I don't really get this. I have tried to find a way to understand but I really don't- I don't understand where the 0.85 came from. Multiplying powers- again this is a question from a rev guide- 4*8=32, but 4*8=2₂* 2₃=2₅ =32 I don't understand how 2 to the power of 3 is 8,

Percentage Decrease: Question from GCSE - 243 / 9 =7, but 243 / 9 = 3₅ / 3₂ = 3₃= 27

Can you please explain all these questions to me, sorry that I'm asking to many questions but please can you answer them, this is the only thing I'm struggling on. Thank You 😀