1. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 (For help, go to Lesson 2-1.) 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 Bell Work # 9

2. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Solutions 1.3 + 4 – 42.7 + 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. Vocabulary and Concepts Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 Subtraction Property of Equality You can subtract the same number from each side of an equation Quick Check 2-5 Vocabulary ArithmeticAlgebra 10= 2( 5 ) if a = b 10 – 5 = 2( 5 ) - _____ then a – c = b - _____ c 5

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

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

6. 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. Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 target numberWordsplusis250number to buy =number to buy.xLet Equation 327+x250= 2-5

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

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

9. Marcy’s CD player cost $113 less than her DVD player. Her CD player cost $78. How much did her DVD player cost? Solving Equations by Adding or Subtracting PRE-ALGEBRA LESSON 2-5 80 = t – 110 80 + 110 = t – 110 + 110 Add 110 to each side. 190 = tSimplify. Marcy’s DVD player cost $190. cost of CD player$113cost of DVD playerWordsless thanwas t=cost of the DVD player.Let t 110 Equation80=– 2-5 Quick Check

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? 5 mi 4–6 31 2-5