Max Rescues the Birthday Party: Addition-Subtraction Challenge!

About this Grade 3 Mixed Add Subtract Drill

By third grade, students need to move beyond single-operation problems and tackle mixed addition and subtraction in a single equation. This skill bridges the gap between basic facts and multi-step thinking—the foundation for algebra and real-world problem-solving. When your child plans a birthday party, they're naturally using this skill: starting with 20 cupcakes, subtracting 8 eaten, then adding 12 homemade ones. Mixed operations require students to process problems left to right, manage two different actions, and track a running total. This builds numerical flexibility and working memory, both critical for upper elementary math success. Practicing these drills strengthens automaticity so that students can solve without counting on fingers, freeing up mental energy for more complex concepts.

What your student will practice

• Solve mixed addition and subtraction problems in left-to-right order
• Maintain accuracy across two operations within a single equation
• Build fluency and automaticity with facts up to 20
• Apply mixed operations to simple word problem scenarios

Common mistakes to watch for

The most common error at this stage is operating in the wrong order—students add or subtract whichever number they see first, regardless of sequence. For example, with 15 - 3 + 5, they might compute 15 + 5 first, then subtract 3, getting 17 instead of 17. Another frequent mistake is losing track of the running total after the first operation, essentially forgetting the intermediate answer before applying the second step. Watch for students who rewrite the problem or skip the middle step on paper—these are signs they're not holding the running total in memory. If a child consistently answers correctly for single operations but struggles here, the issue is almost always order of operations or memory load, not basic fact knowledge.