7th Grade Math

30 Expressions and Patterns

Multiplication can be indicated by using parentheses.

Use Order of Operations

Evaluate 14 + 3 ( 7 - 2 ). Justify each step.

14 + 3 ( 7 - 2 ) = 14 + 3 ( 5 ) Subtract 2 from 7.

= 14 + 15 Multiply 3 and 5.

= 29 Add 14 and 15.

c. 20 - 2 ( 4 - 1 ) · 3 d. 6 + 8 ÷ 2 + 2 ( 3 - 1 )

MONEY Julian orders 3 rolls of crepe Item Unit Cost

crepe paper $2

favors $7

balloons $5

paper, 4 boxes of balloons, and 2 boxes

of favors for the school dance. What is

the total cost?

Words

Expression

cost of 3 rolls + cost of 4 boxes + cost of 2 boxes

of crepe paper of balloons of favors

3 × 2 + 4 × 5 + 2 × 7

3 × 2 + 4 × 5 + 2 × 7 = 6 + 20 + 14 Multiply from left to right.

= 40 Add.

The total cost is $40.

e. MONEY Write and evaluate an expression to find the total cost

of 12 rolls of crepe paper, 3 boxes of balloons, and 3 boxes of

favors.

Real-World Link

Crepe paper originated

in the late 1700s.

RRR

C

Examples 1–3 Evaluate each expression. Justify each step.

1. 8 + (5 - 2) 2. 25 ÷ (9 - 4)


2. 14 - 2 · 6 + 9 4. 8 · 5 - 4 · 3


3. 4 × 10 2 6. 45 ÷ (4 - 1)^2


4. 17 + 2(6 - 3) - 3 × 4 8. 22 - 3(8 - 2) + 12 ÷ 4

Example 4 99 COINS Roy has 3 nickels, 2 quarters, 2 dimes, and 7 pennies. Write and

evaluate an expression to find how much money he has.

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