My daughter, Emily, wants to have a birthday party.  I told her that she should have less than 12 children at her party.  She plans to include her 2 older sisters and of course, herself.  How many children could she invite to her party?  
                3  +  ?  <  12     This is called an inequality and sometimes there is more than one answer.
Hint:  < is less than
           > is greater than

Try to solve the following inequalities:

   4  +  ?  >  10

  11  -  ?  <  5

  6  +  7  <  ?  +  1

For 4th and 5th graders:  Solve the following inequalities:

    24 + 56 > 75 + ?

  103 - 54 < ? + 2

  sides on a pentagon  x  inches in a foot < sides on a hexagon  x  ?