7th Grade Math

Addition and Subtraction Equations

PART A B C D

Main Idea

Solve one-step

equations using

models.

Multi-Part

Lesson 1

Get ConnectED

GLE 0706.3.7 Use

mathematical models

involving linear equations

to analyze real-world

phenomena. GLE 0706.3.8

Use a variety of strategies to

efficiently solve linear

equations and inequalities.

Also addresses GLE 0706.1.4,

GLE 0706.1.8, SPI 0706.3.7.

206 Equations and Inequalities

Solve Equations Using

Algebra Tiles

On the balance at the right,

the paper bag contains a certain

number of orange blocks.

(Assume that the paper bag

weighs nothing.) Without looking

in the bag, how can you determine

the number of blocks it contains?

One way is to remove 4 blocks

from each side of the balance. So,

the bag contains 3 blocks.

In algebra, an equation is like a balance. The weights on each side of the

scale are equal. The expressions on each side of an equation are equal.

You can use algebra tiles to model and solve equations.

Solve x + 4 = 7 using algebra tiles.

Model the equation.

1 =

1 1

(^11)
1 1
1
1
1
x 1
x + 4 = 7
Remove the same
x =
1
1
1
1
1 1
1 1
1 1
1
x + 4 - 4 = 7 - 4
number of 1-tiles
from each side of
the mat so that the
variable is by itself
on one side.
The number of
x = 1
1
1
x = 3
1-tiles remaining
on the right side of
the mat represents
the value of x.
Therefore, x = 3.
Check Since 3 + 4 = 7, the solution is correct. 
204_213_C04L1_895130.indd 206 12/31/09 3:55 PM