Can a modem that is uses a ethernet cable connected to a wireless PC?

Yes, a modem connected via an Ethernet cable can provide internet access to a wireless PC, but it typically needs to be connected to a router first. The modem connects to the router through the Ethernet cable, and the router then broadcasts a wireless signal that the PC can connect to. If the modem has built-in routing capabilities, it can directly support wireless connections without a separate router.