Reviewing questions 1.9 and 1.10 should hopefully help here.
For 1.29, the procedure will be different depending on whether the base $B$ is even or odd. Think about the examples in 1.9 for $B = 2$ and $B = 3$.
For 1.30, here we can only use one side of the balance (while in 1.10 we could use both sides). Therefore, any amount we want to weigh must be balanced by the weights we have available. Looking at some small examples and patterns can be helpful here too.