1. Solve One-Step Addition and Subtraction EquationsPg

2. Definitions
An equation is a sentence stating that two quantities are equal.
x + 3 = 11
This says that “some variable plus 3 is equal to 11”
You can solve this equation by subtracting 3 from each side of the equation.
x = 8

3. Subtraction Property of Equality
If you subtract the SAME NUMBER from each side of an equation, the two sides remain equal.
If a = b, the a – c = b – c
Numbers
6 = 6
2 = 2
Algebra
x + 7 = 11
x = 4
In Algebra expression, always check your work.
x + 7 = 11, we said x = 4. Substitute 4 in for “x”
4 + 7 = 11
11 = 11

4. Let’s work a few! a + 5 = 21 -5 -5 a = 16 c + 7 = 2 -7 -7 c = -5
Check!
a + 5 = 21
a = 16
c + 7 = 2
c = -5
a + 5 = 21
= 21
21 = 21
c + 7 = 2
= 2
2 = 2

5. Addition Property of Equality
If you add the SAME NUMBER to each side of an equation, the two sides remain equal.
If a = b, then a + c = b + c
Numbers
4 = 4
7 = 7
Algebra
x – 6 = 10
x = 16

6. Let’s work some! Always Check! y – 8 = 2 +8 +8 y = 10 y – 8 = 2
+8 +8
y = 10
4 = d – 3
7 = d
y – 8 = 2
10 – 8 = 2
2 = 2
4 = d – 3
4 = 7 – 3
4 = 4

7. Word Problem
Alice was trying to figure out how many goodie bags to fix for a client. The client said that she would need 4 more than Sally had at her event for a total of 11. How many were at Sally’s event?
Let x = the number of people at Sally’s event.
x + 4 = 11
x = 7
Sally had 7 people at her event.