1. Using inspection, mental math

Eg. a + 4 = 12

8 + 4 = 12

12 = 12

Eg. a + 4 = 12

8 + 4 = 12

12 = 12

Ask yourself what something + 4 = 12 or 12 - something = 4

Try these:

14 = k + 5

14 = 9 + 5

t - 3 = 11

14 - 3 = 11

10 - y = 8

10 - 2 = 8

2. Model (make a picture) and solve

Eg.

Bill rides 4 km to the bridge then rides to work. In total he rides 11 km. How far from the bridge to work?

4 + y = 11

4 + 7 = 11

3. Apply the opposite operation

Eg. c + 22 = 56

- 22 = -22

c = 34

Check- c + 22= 56

34 + 22 = 56

56 = 56

*1st step*- Isolate the variable (get the letter by itself)

*2nd step*- Apply the opposite operation

*3rd step*- Check your answer. Substitute the answer for the letter of the original equation

Opposite operation - An operation that "undoes" another operation

* subtraction and addition are opposites

* division and multiplication are opposites

Solve by applying the opposite operating - Check your answer:

1. n + 7 = 26

- 7 = -7

n = 19

Check - n + 7 = 26

19 +7 = 26

26 = 26

2. d - 3 = -5

+3 = +3

d = -2

Check - d - 3 = -5

(-2) - 3 = -5

-5 = -5

Page 398-401 # 1-22 is HOMEWORK!

http://www.mytextbook.ca/