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Solving Equations by Adding or Subtracting

Solving Equations by Adding or Subtracting. PRE-ALGEBRA LESSON 2-5. (For help, go to Lesson 2-1.). Bell Work # 9. Simplify each expression. 1. 3 + 4 – 4 2. 7 + 9 – 7 3. 8 – 2 + 2 4. 6 + 2 – 2. Check Skills You’ll Need. 2-5. Solving Equations by Adding or Subtracting.

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Solving Equations by Adding or Subtracting

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  1. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 (For help, go to Lesson 2-1.) Bell Work # 9 Simplify each expression. 1. 3 + 4 – 4 2. 7 + 9 – 7 3. 8 – 2 + 2 4. 6 + 2 – 2 Check Skills You’ll Need 2-5

  2. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Solutions 1. 3 + 4 – 4 2. 7 + 9 – 7 = 3 + (4 – 4) = 9 + (7 – 7) = 3 + 0 = 9 + 0 = 3 = 9 3. 8 – 2 + 2 4. 6 + 2 – 2 = 8 + (2 – 2) = 6 + (2 – 2) = 8 + 0 = 6 + 0 = 8 = 6 2-5

  3. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Vocabulary Vocabulary and Concepts Subtraction Property of Equality You can subtract the same number from each side of an equation Arithmetic Algebra • = 2( 5 ) if a = b 5 c 10 – 5 = 2( 5 ) - _____ then a – c = b - _____ Quick Check 2-5

  4. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Vocabulary Addition Property of Equality You can add the same number from each side of an equation Arithmetic Algebra 8 = 2( 4 ) if a = b 3 c 8 + 3 = 2( 4 ) + _____ then a + c = b + _____ Inverse Operations ____________________ are operations that undo each other Quick Check 2-5

  5. y + 5 = 13 Subtract 5 y + 5 – 5 = 13 – 5from each side. – 5 = – 5 Check y + 5 = 13 8 + 5 13 Replace y with 8. 13 = 13 Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Solve y + 5 = 13. Method 1 Method 2 y + 5 = 13 y = 8 Simplify. y = 8 Quick Check 2-5

  6. Words target number is 250 plus number to buy Let x = number to buy. 327 = 250 + x Equation Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Larissa wants to increase the number of books in her collection to 327 books. She has 250 books now. Find the number of books she needs to buy. 2-5

  7. Check  Is the answer reasonable? 250 plus the number of books bought should be a total collection of 327. 250 + 77 = 327 Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 (continued) 327 = 250 + x 327 = x + 250 Use the Commutative Property of Addition. 327 – 250 = x + 250 – 250Subtract 250 from each side. 77 = xSimplify. Larissa needs to buy 77 more books. Quick Check 2-5

  8. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Solve c – 23 = – 40. c – 23 = – 40 c – 23 + 23 = – 40 + 23Add 23 to each side. c = –17 Simplify. Quick Check 2-5

  9. Words cost of CD player was $113 less than cost of DVD player t Let = cost of the DVD player. Equation 80 = t – 110 Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Marcy’s CD player cost $113 less than her DVD player. Her CD player cost $78. How much did her DVD player cost? 80 = t – 110 80 + 110 = t – 110 + 110 Add 110 to each side. 190 = tSimplify. Marcy’s DVD player cost $190. Quick Check 2-5

  10. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Solve each equation. 1.y + 8 = 12 2. 7 + f – 21 = –20 3. 67 = g – (–36) 4. Ricky rides his bike 12 miles every day. He stops after 7 miles to rest. How much farther does he have to ride? 4 –6 31 5 mi 2-5

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