Course 1

2-5 Solving Subtraction Equations

Course 1

Warm UpWarm Up

Lesson PresentationLesson PresentationProblem of the DayProblem of the Day

Warm UpSimplify.

1. x + 7 = 222. 18 + x = 1053. 16 = x + 94. 23 = x + 4

x = 15x = 87

x = 7x = 19

2-5 Solving Subtraction Equations

Course 1

Problem of the DayBruce has 25 CD’s remaining after giving 14 to John, 17 to Mary, and 25 to Sue. How many CD’s did he begin with? 81

Solving Subtraction Equations 2-5 Solving Subtraction Equations

Course 1

Learn to solve whole-number subtraction equations.

2-5 Solving Subtraction Equations

Course 1

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

2-5 Solving Subtraction Equations

Course 1

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 = 51Abraham Lincoln was 51 years old when he became president.

2-5 Solving Subtraction Equations

Course 1

y – 23 = 39 23 is subtracted from y.+ 23

y = 62Add 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?

Additional Example 1A: Solving Subtraction Equations

62 – 23 = 39?

+ 23

2-5 Solving Subtraction Equations

Course 1

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

93 = sAdd 15 to both sides to undo the subtraction.

Check 78 = s – 15Substitute 93 for s in the equation.

Solve 78 = s – 15. Check your answer.

93 is the solution.78 = 78?

Additional Example 1B: Solving Subtraction Equations

78 = 93 – 15?

+ 15

2-5 Solving Subtraction Equations

Course 1

z – 3 = 12 3 is subtracted from z.+ 3

z = 15Add 3 to both sides to undo the subtraction.

Check z – 3 = 12Substitute 15 for z in the equation.

Solve z – 3 = 12. Check your answer.

15 is the solution.12 = 12?

Additional Example 1C: Solving Subtraction Equations

15 – 3 = 12?

+ 3

2-5 Solving Subtraction Equations

Course 1

a – 4 = 7 4 is subtracted from a.+ 4

a = 11Add 4 to both sides to undo the subtraction.

Check a – 4 = 7Substitute 11 for a in the equation.

Solve a – 4 = 7. Check your answer.

11 is the solution.7 = 7?

11 – 4 = 7?

+ 4

Try This: Example 1A

2-5 Solving Subtraction Equations

Course 1

57 = c – 13 13 is subtracted from c.+ 13

70 = cAdd 13 to both sides to undo the subtraction.

Check 57 = c – 13Substitute 70 for c in the equation.

Solve 57 = c – 13. Check your answer.

70 is the solution.57 = 57?

57 = 70 – 13?

+ 13

Try This: Example 1B

2-5 Solving Subtraction Equations

Course 1

g – 62 = 14 62 is subtracted from g.+ 62g = 76

Add 62 to both sides to undo the subtraction.

Check g – 62 = 14Substitute 76 for g in the equation.

Solve g – 62 = 14. Check your answer.

76 is the solution.14 = 14?

76 – 62 = 14?

+ 62

Try This: Example 1C

2-5 Solving Subtraction Equations

Course 1

1. x – 9 = 212. 14 = x – 33. x – 7 = 114. 16 = x – 145. x – 9 = 11

Lesson Quiz

6. Susan is taller than James. The difference in their height is 4 inches. James is 62 inches tall. How tall is Susan?

x = 30x = 17x = 18x = 30x = 20

66 inches

2-5 Solving Subtraction Equations

Course 1