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## Solving Equations by Adding or Subtracting

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**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 Lesson 2-5 Additional Examples Solve y + 5 = 13. Method 1: Method 2: y + 5 = 13 y = 8 Simplify. y = 8**Words**target number is 250 plus number to buy Let x = number to buy. 327 = 250 + x Equation Solving Equations by Adding or Subtracting Lesson 2-5 Additional Examples 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.**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 Lesson 2-5 Additional Examples (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.**Solving Equations by Adding or Subtracting**Lesson 2-5 Additional Examples Solve c – 23 = – 40. c – 23 = – 40 c – 23 + 23 = – 40 + 23Add 23 to each side. c = –17 Simplify.**Words**cost of CD player was $115 less than cost of DVD player t Let = cost of the DVD player. Equation 78 = t – 115 Solving Equations by Adding or Subtracting Lesson 2-5 Additional Examples Marcy’s CD player cost $115 less than her DVD player. Her CD player cost $78. How much did her DVD player cost? 78 = t – 115 Write an equation. 78 + 115 = t – 115 + 115 Add 115 to each side. 193 = tSimplify. Marcy’s DVD player cost $193.