$1.$ Use bitwise and operation to determine network address for a given IP address.

a$.$ Look at the subnet mask and count the $1$s in its binary gives $26$ bits.

Network Parameters ANDing operation

IP Address:

$172\mathrm{.}16\mathrm{.}145\mathrm{.}29$

Subnet Mask:

$255\mathrm{.}255\mathrm{.}0\mathrm{.}0$

Network Address:

Network Parameters ANDing operation

IP Address:

$192\mathrm{.}168\mathrm{.}68\mathrm{.}210$

Subnet Mask:

Network Address:

$192\mathrm{.}168\mathrm{.}68\mathrm{.}128$

Network Parameters ANDing operation

IP Address:

$192\mathrm{.}168\mathrm{.}10\mathrm{.}10$

Subnet Mask:

$255\mathrm{.}255\mathrm{.}255\mathrm{.}0$

Network Address:

Network Parameters ANDing operation

IP Address:

$10\mathrm{.}172\mathrm{.}2\mathrm{.}8$

Subnet Mask:

Network Address:

$10\mathrm{.}160\mathrm{.}0\mathrm{.}0$