Page 162 - Basic College Mathematics with Early Integers

S E C T I O N 2.4 I SUBTRACTING INTEGERS 139

Solve.

81. The difference between a country’s exports and 82. In 2007, the United States exported 511 million
imports is called the country’s trade balance. In 2007, barrels of petroleum products and imported
the United States had $1646 billion in exports and 1241 million barrels of petroleum products.What
$2346 billion in imports.What was the U.S. trade was the U.S. trade balance for petroleum products
balance in 2007? (Source: U.S. Department of in 2007? (Source: U.S. Energy Information
Commerce) Administration)

Mixed Practice—Translating (Sections 2.3, 2.4) Translate each phrase to an algebraic expression. Use “x”
to represent “a number.”

83. The sum of -5 and a number. 84. The difference of -3 and a number.

85. Subtract a number from -20. 86. Add a number and -36.

Review

Multiply or divide as indicated. See Sections 1.6 and 1.7.
100 96 23 51
87. 88. 89. 90.
20 3 * 46 * 89

Concept Extensions

91. Name two numbers whose difference is -3. 92. Name two numbers whose difference is -10.

Each calculation below is incorrect. Find the error and correctly calculate. See the Concept Check in this section.

93. 9 - 1-72 2 94. -4 - 8 4

95. 10 - 30 20 96. -3 - 1-102 -13

Simplify. (Hint: Find the absolute values first.)

99. ƒ -6ƒ - ƒ6ƒ
97. ƒ -3ƒ - ƒ -7ƒ 98. ƒ -12ƒ - ƒ -5ƒ

102. ƒ -23ƒ - ƒ -42ƒ
100. ƒ -9ƒ - ƒ9ƒ 101. ƒ -17ƒ - ƒ -29ƒ

For Exercises 103 and 104, determine whether each statement is true or false.

103. ƒ -8 - 3ƒ = 8 - 3 104. ƒ -2 - 1-62ƒ = ƒ -2ƒ - ƒ -6ƒ

105. In your own words, explain how to subtract one 106. A student explains to you that the first step to
#
signed number from another. simplify 8 + 12 5 - 100 is to add 8 and 12.
Is the student correct? Explain why or why not.