12 -4 -90 73. -2 71. 75. 6 77. 79. 6 0 72. 30 -5 74. - 55 -5 76. 3 78. - 1 7 , a- b 2 9 80. - 2 81. 6 , a- b 5 In Exercises 83–100, use the order of operations to simplify each expression. 83. 4(-5) - 6(- 3) 84. 8(- 3) - 5(- 6) 85. 3(-2)2 - 4(-3)2 86. 5(- 3)2 - 2(- 2)2 87. 82 - 16 , 22 # 4 - 3 89. 5#2 - 3 2 [32 - (- 2)] 2 88. 102 - 100 , 52 # 2 - 3 10 , 2 + 3 # 4 90. (12 - 3 # 2)2 91. 8 - 3[-2(2 - 5) - 4(8 - 6)] 35. 3 - 15 36. 4 - 20 92. 8 - 3[-2(5 - 7) - 5(4 - 2)] 37. 8 - (- 10) 38. 7 - (-13) 39.

How does the model value for 2010 compare with the actual data value shown in 2010. 2? 6 Ch a p t e r 1 Algebra, Mathematical Models, and Problem Solving Sometimes a mathematical model gives an estimate that is not a good approximation or is extended to include values of the variable that do not make sense. In these cases, we say that model breakdown has occurred. Models that accurately describe data for the past ten years might not serve as reliable predictions for what can reasonably be expected to occur in the future.

1) 68. (- 1)35 1. - 7 2. -10 3. 4 4. 13 5. 6 6. 3 1 3 69. - a- b 2 1 3 70. - a- b 4 p 7. ` ` 2 p 8. ` ` 3 9. 0 - 22 0 11. - ` - 2 ` 5 10. 0 - 23 0 12. - ` - In Exercises 13–28, add as indicated. 7 ` 10 13. -3 + (- 8) 14. -5 + (-10) 15. -14 + 10 16. -15 + 6 17. 3 18. 4 19. 11 3 + a- b 15 5 21. - 2 3 - 9 4 20. 7 4 + a- b 10 5 22. - 3 4 - 5 7 23. 5) 24. 9) 25. 4) 26. 3) 27. 4) 28. 3) In Exercises 29–34, find -x for the given value of x. 29. x = 11 30. x = 13 31. x = -5 33. x = 0 32.