1. EXAMPLE 1 Following Order of Operations Music You buy a used guitar for $50. You then pay $10 for each of five guitar lessons. The total cost can be found by evaluating the expression 50 + 10 5. Is the total cost $100 or $300 ?

2. = 50 + 50 EXAMPLE 1 To find the guitar costs described, evaluate 50 + 10 5. 50 + 10 5 First multiply 10 and 5. = 100 Then add 50 and 50. ANSWER The total cost is $100. Following Order of Operations

3. EXAMPLE 2 Evaluating a Variable Expression Substitute 25 for x and 2 for y. Evaluate the power. Multiply 8 and 3. = 1 Subtract 24 from 25. x 3y 3 – = 25 3(2 3 ) – = 25 3(8) – = 25 24 – Evaluate x 3y 3 when x = 25 and y = 2. –

4. GUIDED PRACTICE for Examples 1 and 2 Evaluate the expression. 1. 5 + 6 5 35 ANSWER 2. 20 4 2 2 – 12 ANSWER 3. 10 3 + 3 3 57 ANSWER

5. GUIDED PRACTICE 4. Evaluate a + 4b 2 when a = 6 and b = 5. 106 ANSWER for Examples 1 and 2