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# Single-Variable Expressions Practice Questions (page 3)

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Updated on Oct 3, 2011

#### Practice 3

1. Add y and 11y by adding the coefficients and keeping the base and exponent: 1 + 11 = 12, so y + 11y = 12y.   Replace y with 6 and multiply:

12(6) = 72

2. Subtract 8n from 12n. Remember, subtract the coefficient of 8n from the coefficient of 12n and keep the base and exponent:

12n – 8n = 4n

The expression is now 4n + 7.

Replace n with 9:

4(9) + 7

Multiplication comes before addition in the order of operations:

4(9) = 36

The expression is now 36 + 7.

Add: 36 + 7 = 43.

3. Add 2r2 and 3r2 by adding the coefficients and keeping the base and exponent:   2r2 + 3r2 = 5r2

Replace r with –3:   5(–3)2

Exponents come before multiplication in the order of operations:   (–3)2 = 9   The expression is now 5(9).

Multiply: 5(9) = 45.

4. Replace every h with 4:

4(4) – 8(4) + 6((4) + 2)

Begin with addition inside the parentheses:

4 + 2 = 6

The expression is now:

4(4) – 8(4) + 6(6)

Multiplication comes before subtraction or addition, so multiply next:

4(4) = 16

8(4) = 32

6(6) = 36

The expression is now:

16 – 32 + 36

–32 + 36 = 4

The expression is now:

16 + 4

Add: 16 + 4 = 20.

5. None of the terms in the expression 5s + s2 – 9 can be combined because they are unlike terms. Replace every s with –2:   5(–2) + (–2)2 – 9

Work with the exponent first:

(–2)2 = 4

The expression is now:

5(–2) + 4 – 9

Multiplication comes before addition or subtraction, so multiply next:

5(–2) = –10

The expression is now:

–10 + 4 – 9

–10 + 4 = –6

The expression is now:

–6 – 9

Finally, subtract: –6 – 9 = –15.

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