Answer:
price paid of speakers= £40.5
price paid of headphones=£ 5.6
price paid of book=£6.65
price paid of mobile phone=£42
price paid of mouse=£ 15.75
price paid of DVD=£11.05
solution,
1. Cost of speakers:
Discount percent=10 %
Marked price=£45
discount amount= discount % of MP
=10% of 45
=£4.5
Selling price= MP - discount amount
=£45-£4.5
=£ 40.5
2. cost of headphones:
discount amount= discount% of MP
=20% of 7
=£1.4
Selling price= MP- Discount amount
=£7-£1.4
=£ 5.6
3. cost of books:
discount amount= discount percent of MP
= 30% Of 9.50
=£ 2.85
selling price= MP- Discount amount
= £ 9.50-£2.85
=£ 6.65
4. cost of mobile phone:
discount amount= discount% of MP
=40% of 70
=£ 28
selling price= MP- Discount amount
=£70-£28
=£ 42
5. cost of mouse:
discount amount= discount% of MP
= 25% of 21
=£ 5.25
selling price= MP- Discount amount
=£21-£5.25
=£ 15.75
6. cost of DVD:
discount amount= discount % of MP
= 15% of 13
= £ 1.95
selling price= MP- discount amount
=£ 13 -£ 1.95
=£ 11.05
Hope this helps...
Good luck on your assignment..
(the 21 is from 
•84)