1. Solving Addition
and Subtraction
Equations

2. An equation is
a
mathematical
sentence that
contains an

3. The expression on the
left and right side of
the equal sign are
equivalent. One or
both sides may
contain a variable.

4. A variable is a
letter or
symbol that
stands for a
number.

5. To solve an
equation, you must
find what the
variable represents
so that the two
parts are equal.

7. Equations are
like balance
scales. In order
to keep a scale
balanced you
must have the
same amount of
weight on both

8. If I took one block away from the left
side, what would I have to do to keep
the scale from tipping?

9. If I added 6 more apples to the right
side, how could I keep the scale from
tipping?

10. To keep an equation
equal, we must do
exactly the same thing to
each side of the
equation. If we add a
number to one side, we
must add that same
number to the other side
and vice versa.

11. Addition and
subtraction are called
“inverse operations”.

12. Multiplicatio
n and
division are
inverse
operations,
too!

13. for Solving Addition
and Subtraction
Equations

14. 1. Look to
see what
side the
variable is
on.

15. 2. Decide
what
operation
is being
shown.

16. 3. Do the
inverse of
that
operation
to both
sides.

17. 4. Write
what
number
the
variable
stands for

18. 5. Check the
solution by
“substituting” the
number back into
the equation to

19. Example 1 (bar model)
m + 18 = 34
m
18
34
Look for variable
Do the inverse
What number does m represent?
m = 16
Substitute in m
16
18
34
16 + 18 = 34
34 = 34
Solution is correct!

20. Example 1
m + 18 = 34
-18 -18
m = 16
Do the inverse
m + 18 = 34
16 + 18 = 34
34 = 34
substitute in m
Look for variable
Write what m is
Solution is correct!

21. Always remember to
check your solution
to the equation.

22. Example 2
68 = y + 43
-43
-43
Look for variable
25 = y
68 = y + 43
68 = 25 + 43
68 = 68
Write what y is
Do the opposite
Plug in y
Solution is correct!

23. Example 3
t - 14 = 22
+ 14 +14
t = 36
Do the inverse
t - 14 = 22
36 - 14 = 22
22 = 22
Substitute in t
Look for variable
Write what t is
Solution is correct!

24. Try These...
1.
2.
3.
4.
r + 5 = 18
m - 26 = 59
102 = x - 15
a + 39 = 56
r = 13
m = 85
117 = x
a = 17

25. Prediction:
You will show all
of the steps
(including
checking) as you
have been shown
today

26. Are there any
questions
about solving
addition or
subtraction
equations?