8 biscuits cost 24p altogether. How much do 5 cost

In the question the cost of 8 biscuits is already given. Based on that the price of 5 biscuits can be easily deduced.

The cost of 8 biscuits = 24 p

Cost of 1 biscuit = (24/8) p

= 3p

Then

The cost of 5 biscuits = (3 * 5) p

= 15p

Hence the cost of 5 biscuits is 15p. I hope the procedure for finding the correct answer is clear to you. If you closely follow the method of doing this problem, then in future you can do it by yourself.