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 — Use one inverse addition or subtraction operation to isolate the variable.
• 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.
• Subtraction Property of Equality — Subtracting the same amount from both sides keeps an equation balanced.
• Addition Property of Equality — Adding the same amount to both sides keeps an equation balanced.

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.