Can your child find the missing number? This colorful worksheet offers a very gentle introduction to basic algebra. In each problem, your child will reverse the operations, adding for a subtraction problem or subtracting for an addition problem, in order to find the missing number. When he's done, your child will have a better understanding of the relationship between adding and subtracting.
Check out the rest of the worksheets in the Find the Missing Numbers series for more problems like this.
Which set of standards are you looking for?