My Mom Has Been Coughing For Three Weeks Straight. She

My mom has been coughing for three weeks straight. She has been having the hardest time getting sleep. She has mucus that she is coughing up but, it will not fully come out. It get's stuck and she is taking Alka-Seltzer plus for her cough and drinking hot tea. It is still not working. How can this problem be solved?