This is a Smartboard lesson that allows students to practice solving word problems involving adding. All of the sums are 20 or less. Each sum is already given and students need to solve for a missing addend. Each page asks students to come up with the correct number sentence and then to figure out the answer. Both of these are provided on each page. The preview file has thumbnail shots of many of the pages in this lesson. The last page can be used for guided practice without the word problems.