6.EE.7. Solve real-world and mathematical problems by writing and solving equations of the form x + p = q and px = q for cases in which p, q and x are all nonnegative rational numbers.

A cool math game for kids - The Number Monster. Arithmetic practice game for subtraction. Let's you pick what numbers you want to practice with. You can pick math facts from 1-10 or go up to 36 with Yardstick Arithmetic.