Solve exercise 1
Solve exercise 3
Solve exercise 4
Solve exercise 5
Solve exercise 6
Solve exercise 7
Solve exercise 8
Solve exercise 9
Solve exercise 10
Solve exercise 11
Solve exercise 12
Solve exercise 13
Solve exercise 14
Solve exercise 15
Solve exercise 16
Solve exercise 17
Solve exercise 18
Solve exercise 19
Solve exercise 20
Solve exercise 21