Algebra 1 Common Core Student Edition, Grade 8-9

(Marvins-Underground-K-12) #1
What operations are
used in th e equation?
The e q u a tio n uses
multiplication and
a d d itio n. You can undo
the addition first, and
then the m ultiplication.

How can a model
help you w rite the
The m odel show s th a t
a h a lf o f a sheet per ad
plus 5 sheets fo r th e
title banner is equal to
18 sheets.
I- 1 8................. 1

Solving a Two-Step Equation
What is the solution of 2x + 3 = 15?
2x + 3 = 15
Subtract 3 from each side.
Divide each side by 2.

2x + 3 - 3 = 15
2x = 12
2 x

x = 6
Check 2x + 3 = 15
2(6) + 3 = 15
15 = 15

Substitute 6 for x.
Simplify. The solution checks.

^ Got It? 1.W hat is th e solution of 5 = ; 3?

Problem 2 Using an Equation as a M odel

Community Service You are making a bulletin board to advertise community
service opportunities in your town. You plan to use half a sheet of construction
paper for each ad. You need 5 sheets of construction paper for a title banner.
You have 18 sheets of construction paper. How many ads can you make?

  • Paper per ad: j sheet

  • Paper for banner: 5 sheets

  • Total paper: 18 sheets

The num ber o f ads
you can make

W rite and solve an e q u a tio n. Let th e
variable represent the unknown.

Let a = th e n u m b e r of ads you can make.
\a + 5 = 18
\a + 5 - 5 = 18
= 13

Subtract 5 from each side.

Multiply each side by 2.
You can m ake 26 com m unity service advertisem ents for the bulletin board.

2 L a 2(13)
a = 26

G ot It? 2. Suppose you u sed o n e q u a rte r of a sh eet of p a p e r for each ad an d
four full sheets for th e title b a n n e r in Problem 2. How m any ads
could you make?



Lesson 2-2 So l v i n g Tw o - St e p Eq u a t i o n s -
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