Solve one-step addition and subtraction equations with whole numbers
Solving an equation is like solving a mystery! Your goal is to find the value of the unknown variable (like 'x'). To do this, you need to get the variable by itself on one side of the equal sign by using inverse operations.
Concept
An equation is a math sentence that says two things are equal. A one-step equation is an equation that you can solve in only one step. **The Golden Rule of Algebra: Keep the Equation Balanced** Whatever you do to one side of an equation, you **must** do to the other side to keep it balanced. Think of a balanced scale. If you add weight to one side, you must add the same weight to the other side to keep it from tipping. **Solving Addition Equations** To solve an addition equation, you use the inverse operation, which is subtraction. **Example: x + 5 = 12** 1. **Goal:** Get 'x' by itself. 2. **What's with x?** A "+ 5". 3. **Do the inverse:** Subtract 5 from both sides of the equation. * x + 5 - 5 = 12 - 5 4. **Simplify:** * x + 0 = 7 * x = 7 5. **Check your answer:** Plug 7 back into the original equation: 7 + 5 = 12. It's true! **Solving Subtraction Equations** To solve a subtraction equation, you use the inverse operation, which is addition. **Example: y - 8 = 10** 1. **Goal:** Get 'y' by itself. 2. **What's with y?** A "- 8". 3. **Do the inverse:** Add 8 to both sides. * y - 8 + 8 = 10 + 8 4. **Simplify:** * y + 0 = 18 * y = 18 5. **Check your answer:** Plug 18 back in: 18 - 8 = 10. It's true! **Key Idea:** To undo an operation, you do its opposite. The opposite of adding is subtracting. The opposite of subtracting is adding.
Try it
Practice: Solve one-step addition and subtraction equations with whole numbers.