Lesson 2: Solve One-Step Addition and Subtraction Equations6.AT.8

I can…

I can solve one-step addition and subtraction equations using inverse operations.

Key words

• Equation — A math sentence with an equal sign showing both sides are the same.
• Inverse operation — Two math actions that undo each other, like × and ÷.
• Isolate — To get the letter by itself on one side.
• Solution — A number that makes the equation or inequality true.
• One-step equation — An equation you can solve in a single step using one inverse operation.
• Balance — Keeping both sides of an equation equal by doing the same thing to each side.

Steps

1. Solve n + 23 = 58. The 23 is added to n.
2. The inverse of adding 23 is subtracting 23.
3. I subtract 23 from both sides: n + 23 − 23 = 58 − 23.
4. That leaves n = 35. Check: 35 + 23 = 58. True!

Try it

Solve: p + 2.8 = 9.1

Check your answer

p = 6.3

Subtract 2.8 from both sides: p = 9.1 − 2.8 = 6.3. Check: 6.3 + 2.8 = 9.1 ✓ (11.9 comes from adding instead of subtracting; 7.7 comes from subtracting each decimal place without regrouping — 9 − 2 = 7 and, without borrowing, 8 − 1 = 7; 3.25 comes from dividing 9.1 ÷ 2.8 instead of subtracting.)

Sentence starter

I know ___ because ___.

Goal: I can explain my steps using the words equation, inverse operation, isolate, and solution.