Step-by-step explanation: First of all, we need to start with the conversion factor for pounds and ounces which is 16 ounces = 1 pound.
So since we're given that the package weighs 1 pound and 5 ounces, we can rewrite the problem to say the package weighs 16 ounces and 5 ounces. I put 16 since the conversion factor for pounds and ounces.
Now we can add 16 and 5 together to get a sum of 21.