Robin has 28 packages of gum and 13 packages of candy. There are 4 pieces in each package. How many pieces of gum does Robin have?
There are 4 pieces in each package of gum. 
There are 28 packages of gum. 

So, we can multiply 4 by 28 to find out how many pieces of gum Robin has. 

4 x 28 = 112

Robin has 112 pieces of gum.