Let me take a stab at question 1.

128.171.x.x is a class B address, therefore the eight bit subnet will be in the third octet.

So the counting the subnets up I get :-

128.171.0.0 This is the zero subnet not normally acknowledged or required on the CCNA unless specifically asked for so I discount it (please can someone correct me if this wrong!).
128.171.1.0 First subnet
128.171.2.0 Second subnet
128.171.3.0 Third subnet

So I get 128.171.3.2 as the second host on the third subnet.

As for question 2 I think this is more simple. It's a trick question. There can't be a 20 bit network part for the address.

A = 8 network bits. B = 16 network bits C = 24 network bits.

I would therefore have to go with e for this question.

K.

1) a firm is assigned the network part 128.171. It selects an 8-bit subnet part. Represent the second host on the third subnet in dotted decimal notation.

I came up with 128.171.4.2

2) You have a 20-bit network part and a 4-bit subnet part, how many hosts can you have per subnet? a. 14 b. 16 c. 254 d. 256 e. none of the above

I came up with C

Do these answers look right?

Thanks