Louisa has a goal of collecting 100 pounds of dog food for a local shelter. she records how many pounds of food she collects
each week

Louisa needs 28 more pounds of dog food to reach 100 pounds

Step-by-step explanation:

=100 - 20.5 + 18.75 + 32.75

=28

Louisa needs 28 pounds more of dog food.

Step-by-step explanation:

We need to find how much dog food she had collected in three weeks. In order to do this we need to add the number of pound collected in each week.

Notice that the pounds collected are given in different notations, so we need to write them ‘‘uniformly’’, in particular we must write the mixed number of the second week in decimal notation:

Now, we add the three numbers:

Finally, as she wants to collect 100 pounds and already has 72, Louisa only has to collect 28 pound more to complete her goal.