The supply line to the ballcock of a Moen 5351 leaks at the ballcock connection Bought a new supply line; still leaks

HOW TO REPLACE A BALLCOCK ON A WATER CLOSET, COMMODE: FIRST SHUT WATER OFF TO COMMODE. THER WILL BE A WATER SHUTOFF VALVE BETWEEN THE FLOOR AND THE COMMODE ON THE WATER LINE TO YOUR BALLCOCK, TURN WATER OFF, FLUSH COMODE SO YOU CAN CLEAR MOST ALL OF THE WATER OUT OF IT. THEN UNCREW THE NUT FOR THE WATER SUPPLY, THEN UNSREW THE NUT FOR THE BALLCOCK ITSELF, OPEN THE TOP OF THE COMMODE, YOU WILL SEE A FLAPPER ON THE BALLCOCK, REMOVE IT, THEN TAKE THE BALLCOCK OUT, SOME HAVE A ROD AND FLOAT SOME DO NOT, EITHER WAY IF IT DOES WHEN YOU PUT THE BALLCOCK BACK IN THE SAME WAY THE OLD ONE CAME OUT MAKE SURE YOU HAVE THE GASKET ON WHEN YOU STICK THE END OF THE BALLCOCK BACK, TIGHTEN THE NUT, THEN MAKE SURE YOUR WASHER IS IN THE NUT ON THE WATER LINE AND RE CIONNECT WATER LINE, YOU CAN ADUST FLOAT VALVE BY BENDING THE ROD DOWN TO THE AMOUNT OF WATER YOU WILL WANT CONNECT FLAPPER BACK, TO THE NEW BALLCOCK, IF THE BALLCOCK DOES NOT HAVE A FLOAT, YOU CAN ADJUST PER INSTRUCTION, SO AFTER ALL THIS IS DONE AND TUBE IS CONNECTED FROM BALLCOCK TO THE TOP OF IT WITH CLIP, TO DIRECT YOUR FILL WATER, TURN YOUR WATER ON AND ADJUST SOME MORE IF NEED BE, UNTILL YOUR CORRECT AMOUNT OF WATER IS LIKE YOU WANT IT...THIS IS REALLY EASY COMPARED TO PAYING A PLUMBER FOR THIS JOB, AND IT HAS TO BE DONE QUITE OFTEN, LARRY VEAL MASTER PLUMBER TEXAS