AF1.1 Write and solve one-step linear equations in one variable.

1. California Standards AF1.1 Write and solve one-step linear equations in one variable.

2. When John F. Kennedy became president of the United States, he was 43 years old. He was 8 years younger than Abraham Lincoln was when Lincoln became President. How old was Lincoln when he became president?

3. 8 + 8 + 8 Let a represent Abraham Lincoln’s age. Abraham Lincoln’s age John F. Kennedy’s age – = – = a 8 43 a – 8 = 43 a = 51 Abraham Lincoln was 51 years old when he became president.

4. y – 23 = 39 23 is subtracted fromy. + 23 + 23 ? 62 – 23 = 39 ? 39 = 39 Example 1A: Solving Equations by Adding Solve y – 23 = 39. Check your answer. Add 23 to both sides to undo the subtraction. y = 62 Check y – 23 = 39 Substitute 62 fory in the equation.  62 is the solution.

5. 78 = s – 15 15 is subtracted froms. + 15 ? 78 =93 – 15 ? 78 = 78 Example 1B: Solving Equations by Adding Solve 78 = s – 15. Check your answer. Add 15 to both sides to undo the subtraction. + 15 93 = s Check 78=s – 15 Substitute 93 fors in the equation.  93 is the solution.

6. z – 3 = 12 3 is subtracted fromz. + 3 + 3 ? 15 – 3 = 12 ? 12 = 12 Example 1C: Solving Equations by Adding Solve z – 3 = 12. Check your answer. Add 3 to both sides to undo the subtraction. z = 15 Check z – 3 = 12 Substitute 15 forz in the equation.  15 is the solution.

7. 57 = c – 13 13 is subtracted fromc. + 13 + 13 ? 57 = 70 – 13 ? 57 = 57 Check It Out! Example 1 Solve 57 = c – 13. Check your answer. Add 13 to both sides to undo the subtraction. 70 = c Check 57=c – 13 Substitute 70 forc in the equation.  70 is the solution.