Holt CA Course 1

1-9 Solving Equations by Adding

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

California Standards

Holt CA Course 1

1-9 Solving Equations by Adding

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?

Holt CA Course 1

1-9 Solving Equations by Adding

Abraham Lincoln’s age

John F. Kennedy’s age– = 8

Let a represent Abraham Lincoln’s age.

a – =8 43

a – 8 = 43

+ 8 + 8

a = 51

Abraham Lincoln was 51 years old when he became president.

Holt CA Course 1

1-9 Solving Equations by Adding

y – 23 = 39 23 is subtracted from y.

+ 23

y = 62

Add 23 to both sides to undo the subtraction.

Check y – 23 = 39Substitute 62 for y in the equation.

Solve y – 23 = 39. Check your answer.

62 is the solution.39 = 39?

Example 1A: Solving Equations by Adding

62 – 23 = 39?

+ 23

Holt CA Course 1

1-9 Solving Equations by Adding

78 = s – 15 15 is subtracted from s.+ 15

93 = s

Add 15 to both sides to undo the subtraction.

Check 78 = s – 15

Substitute 93 for s in the equation.

Solve 78 = s – 15. Check your answer.

93 is the solution.78 = 78?

Example 1B: Solving Equations by Adding

78 = 93 – 15?

+ 15

Holt CA Course 1

1-9 Solving Equations by Adding

z – 3 = 12 3 is subtracted from z.+ 3

z = 15

Add 3 to both sides to undo the subtraction.

Check z – 3 = 12

Substitute 15 for z in the equation.

Solve z – 3 = 12. Check your answer.

15 is the solution.12 = 12?

Example 1C: Solving Equations by Adding

15 – 3 = 12?

+ 3

Holt CA Course 1

1-9 Solving Equations by Adding

57 = c – 13 13 is subtracted from c.

+ 13

70 = c

Add 13 to both sides to undo the subtraction.

Check 57 = c – 13

Substitute 70 for c in the equation.

Solve 57 = c – 13. Check your answer.

70 is the solution.57 = 57?

57 = 70 – 13?

+ 13

Check It Out! Example 1