can an expert help with this

Jasmine sells bracelet for "b" to a shop
The shop adds £6.20 to "b" and then sells it at that price. Therefore, the store's profit is £6.20 every time they sell one bracelet.
If the shop makes 80% profit on each bracelet, that means the £6.20 is 80% of the expense they incurred when they buy the bracelet off of Jasmine, in other words, 80% of "b".
So:
6.20 = .8b
b = £7.75
PART B:
Jasmine has 7 1/2 hours or 450 minutes to finish her duties for the fashion show.
For 15 necklaces that require 24 minutes each, that is a total of 15x24 = 360 minutes total to build the necklaces.
The show is 40 miles away. We assume she will travel the maximum 50 mph. So it will take her 40/50 hour or 4/5 hour or 48 minutes to get there.
She also allows 30 minutes for breaks. I'm not sure what this means, but I'm guessing she wants a 30 minute break somewhere in her day so she can get some rest. So we will include the 30 minutes as a requirement.
Therefore, it will take Jasmine 360 + 48 + 30 = 438 minutes in total.
She has 450 minutes available, thus she will be 450-438 = 12 minutes under the deadline.