1. Equations and Inequalities

2. Unit 8 – Solving Addition and Subtraction Equations Algebraically

3. Vocabulary Isolate – to set apart.
Inverse Operation – an operation that is the opposite of, or undoes, another operation; addition and subtraction are inverse operations; multiplication and division are inverse operations.

4. Solving Subtraction Equations Algebraically - Example
Solve algebraically for x , then check.
Solve
x – 12 = 23
x = 35
We added 12 to both sides because there was a -12 on the same side as the x and you do the opposite to eliminate (get rid of) a term.
Check
x – 12 = 23
(35) – 12 = 23
23 = 23
If the final line is correct, you have the right value for x. If it is not correct, go back to the work you did to solve for x and start again.

5. Solving Subtraction Equations Algebraically - Example
Solve algebraically for x , then check.
Solve
x – 15 = 47
x = 62
Check x – 15 = 47 (62) – 15 = = 47

6. Solving Addition Equations Algebraically - Example
Solve algebraically for x , then check.
Solve
x = 139 _
x = 114
Check x + 25 = 139 (114) + 25 = = 139

7. Solving Addition Equations Algebraically - Example
Solve algebraically for x , then check.
Solve
34 + x = 42
34 + x = 42
x = 8
Check 34 + x = (8) = = 42

8. Solving Addition & Subtraction Equations Algebraically - Practice
Solve algebraically, then check.
y + 13 = 84
y = 71
z – 14 = 54
z = 68
t = 55
t = 49
u – 24 = 82
u = 106

9. More Solving Addition & Subtraction Equations Algebraically - Practice
Solve algebraically, then check.
y = 24.39
y = 11.79
z – = 3 3 5
z =
14.86 = t – 8.3
t = 23.16
= u
u =