#4, p. 408:

Log[1/Exp[1]]
Log[10,Sqrt[10]]

#20, p. 409

Plot[{Log[x]/Log[2],Log[x]/Log[4],Log[x]/Log[6],Log[x]/Log[8]},{x,0,4}]

#28, p. 409:

Solve[Log[x^2-1]==3,x]
Solve[Exp[2x]-3*Exp[x]+2==0,x]