can you increase water pressure in city water line to house by hooking up a pressure tank in line?

No if it's 80 psi. coming in it will still be 80 psi. but it might help maintain a steady 80 psi. thought the house.

City water pressure can be increased by adding a pump with pressure switch and pressure tank in line. This is not normally necessary as most city water pressures range from 35 to 100 psi. If your city water pressure is low, I suggest you contact the water company and have them put a booster station in your neighborhood. Your neighbors must have the same low pressure as you, so that would warrant a booster station.

I don't think so. I believe that would take a pressure tank plus a boost pump.