Exercise 1: A Device on 10.0.1.0/24 Reaching 10.0.9.5 — Possible Solution
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Step-by-step, per the chapter's own logic:

1. The device compares the destination address (10.0.9.5) against its
own subnet, 10.0.1.0/24. Per the chapter, "the device compares the
destination IP against its own subnet mask." A /24 mask means only
the first three octets (10.0.1) define the local network -- and the
destination's own third octet is 9, not 1, so 10.0.9.5 does NOT fall
within the device's own 10.0.1.0/24 subnet.

2. Because the destination is off-subnet, the device does not attempt
local, direct delivery at all. Per the chapter, "if the destination
falls outside the local subnet, the packet gets addressed at the Data
Link layer to the default gateway's own MAC address -- but the
destination IP address itself, at the Network layer, stays completely
unchanged." So the device addresses the outgoing frame, at Layer 2, to
its own default gateway's MAC address -- NOT to any MAC address
belonging to 10.0.9.5 directly, since the device has no way to reach
that address's own network segment directly.

3. Critically, the destination IP address inside the packet itself
(10.0.9.5) is never altered during this process -- only the Layer 2
framing changes to point at the gateway. Per the chapter, "the gateway
is only the next physical hop, not the final destination." The packet
still says "deliver this to 10.0.9.5" at the IP layer; it's simply
being handed physically to the gateway first, which is responsible for
figuring out where to send it from there using its own routing table
(a separate step, happening after the packet leaves this device).

So before the packet ever leaves the originating device: it determines
the destination is off-subnet via the subnet-mask comparison, then
addresses the frame to the default gateway's MAC address at Layer 2,
while leaving the actual IP-layer destination (10.0.9.5) untouched.

WHY THIS WORKS AS AN ANSWER
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This walks through the exact sequence the chapter itself describes --
the subnet check, then the Layer 2 vs. Layer 3 addressing distinction
-- rather than skipping straight to "it goes to the gateway" without
explaining what specifically changes and what specifically doesn't.