Some important questions from Johnston 6th edition:

Chapter#1:
1.pages 22-23-24
2.problem 1-55 page 46

Chapter#3:
1. sample problem 3-3 page 156
2. sample problem 3-4 page 157
3. problem 40 page 160
4. problem 45 page 163
5. problem 49 page 163
6. problem 55 page 164
7. problem 56 page 164
8. problem 57 page 165
9. problem 59 page 165
10. problem 63 page 166
11. problem 138 page 194
12. problem 139 page 194
13. problem 141 page 195
14. problem 157 page 204
15. problem 161 page 204

Chapter#4:
1. problem 141 page 272
2. problem 142 page 272

Chapter#5:
1. problem 81 page 323
2. problem 87 page 324

You can also download the PDF file of these question in the link below