Lesson 2: Write and Solve Equations Using Addition or Subtraction6.AT.8

I can…

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

Key words

• Solve One-Step Addition and Subtraction Equations — Undo the + or − to get the letter alone.
• Equation — A math sentence with an equal sign.
• Inverse operation — Two actions that undo each other, like × and ÷.
• Isolate — Get the letter alone on one side.
• Solution — A value that makes the math sentence true.
• One-step equation — An equation you solve with just one step.
• Balance — Doing the same thing to both sides so they stay equal.
• Subtraction Property of Equality — Subtract the same number from both sides. They stay equal.
• Addition Property of Equality — Add the same number to both sides. They stay equal.

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: q + 1.6 = 7.2

Check your answer

q = 5.6

Subtract 1.6 from both sides: q = 7.2 − 1.6 = 5.6. Check: 5.6 + 1.6 = 7.2 ✓

Sentence starter

I know ___ because ___.

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