1. Evaluating an expression with one variable

2. Substituting 2 in place of m, we get
Value of an expression
To find the value of an algebraic expression, we need to substitute the value of the variable in the algebraic expression
For example: Value of m + 8 for m = 2 will be
m+8
Substituting 2 in place of m, we get
(2) + 8 = 10

3. Substituting the value 7 for b, we get
Example 1: Find a value for the expression 3b when b =7 3b
Substituting the value 7 for b, we get
3b =
3 x (7)
= 21
Take out b and replace it with 7
Put 7 inside a bracket
21 is the value of the expression
Ans: 21

4. Substituting the value 8 for x, we get
Example 2: Find a value for the expression x - 20 when x =8
x-20
Substituting the value 8 for x, we get
x-20 =
(8) - 20
= -12
-12 is the value of the expression
Take out x and replace it with 8
Put 8 inside a bracket
Ans: -12

5. Try these Find the value for the expression. a) x + 8 when x = 3
b) 12y when y = 2