1. Learn to plug in variables to solve problems.

2. A variable is a letter that represents a number that can change.
The coefficient is the number that doesn’t change in a problem
Coefficient
Variable

3. Additional Examples 1A and 1B: Evaluating Algebraic Expressions with One Variable
Evaluate each expression for the given value of the variable.
A. x – 5 for x = 12
12 – 5
Substitute 12 for x. 7
Subtract.
B. x + 5 for x = 3
3 + 5
Substitute 3 for x. 8
Add.

4. Additional Examples 1A and 1B: Evaluating Algebraic Expressions with One Variable
Evaluate each expression for the given value of the variable.
A. 4c + 1 for c = 11
4(11) + 1
Substitute 11 for c.
44 + 1
Multiply. 45
Add.
B. 10 – 2y for y = 4
10 - 2(4)
Substitute 4 for y.
10 – 8
Multiply. 2
Subtract.

5. Additional Example 1C: Evaluating Algebraic Expressions with One Variable
Evaluate the expression for the given values of the variable.
C. 6(n + 2) – 4 for n = 5, 6, 7 5 6 7
n Substitute Parentheses Multiply Subtract
6(5 + 2) – 4
6(7) – 4
42 – 4 38
6(6 + 2) – 4
6(8) – 4
48 – 4 44
6(7 + 2) – 4
6(9) – 4
54 – 4 50

6. Try This: Example 1C
Evaluate the expression for the given values of the variable.
C. 5(n + 3) – 2 for n = 3, 4, 5 3 4 5
n Substitute Parentheses Multiply Subtract
5(3 + 3) – 2
5(6) – 2
30 – 2 28
5(4 + 3) – 2
5(7) – 2
35 – 2 33
5(5 + 3) – 2
5(8) – 2
40 – 2 38

7. Additional Example 2: Evaluating Algebraic Expressions with Two Variables
Evaluate each expression for the given value of the variables.
A. 4x + 3y for x = 2 and y = 1
4(2) + 3(1)
Substitute 2 for x and 1 for y.
8 + 3
Multiply. 11
Add.
B. 8r – 2p for r = 2 and p = 5
8(2) – 2(5)
Substitute 2 for r and 5.5 for p.
16 – 10
Multiply. 6
Subtract.

8. Additional Example 3A: Physical Science Application
Use the expression 1.8c + 32 to convert the boiling point temperature from degrees Celsius to degrees Fahrenheit.
A. Boiling point of water at sea level: 100°C
1.8c + 32
1.8(100) + 32
Substitute 100 for c.
Multiply.
212
Add.
100°C = 212°F
Water boils at 212°F.