Requiring only a couple of wrenches and less than a half-hour of your time, replacing the flexible water supply hose to a toilet is a task easily completed by even a beginning home handyman.
Shut off the supply line valve. This valve is located on the supply pipe to the toilet.
Flush the toilet. This will remove most of the water in the toilet tank. Remove the remaining water with rags or a wet-dry vacuum cleaner such as a Shop-Vac.
Place a small container on the floor under the supply valve. This is to catch any water remaining in the flexible supply line when it is disconnected.
Using either open-end or adjustable wrenches, hold the supply valve with one wrench and loosen the fitting to the flexible supply line where it attaches to the valve with another. The fitting will loosen when turned in a counterclockwise direction. Continue to turn until the fitting is removed from the valve.
Look at the toilet tank end of the flexible supply hose. If necessary, use the two wrenches to loosen and remove this end of the supply hose. The wrenches may not be needed on this fitting, however, as some flexible supply tubes are fitted with a plastic fitting which has built-in wings which allow it to be tightened or loosened without tools.
Replace the flexible supply hose with one of similar length and which also has the same fittings on both ends as the old hose does. Be sure to start the threads on the fittings with your fingers until they are screwed on straight and have turned on several threads.
Tighten the fittings securely but do not overtighten. Doing so could strip the threads.
Turn on the water supply and check for leaks. Tighten any leaking fitting just enough more to stop the leak.