Your ISP has given you an IP block for your use. The block is 192.168.112.64/26.

If your network administrator uses the first usable IP for the router he’s installed on your network, how many usable IPs do you have left?

Answer: 61

Explanation/Reference:
CIDR notation /26 means you have 6 bits left as Host-IDs (32-26=6). The maximum number consisting of 6 Bits is 63 (00111111b) giving you 64 Hosts (including 0). You have to remove 2 IPs for Net-ID and Broadcast-ID and 1 for the Router. 64 – 3 = 61.