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Modeling and Solving
Two-Step Equations
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SEVENTH GRADE MATH
Moving Straight Ahead
Investigation 4.2
A.The first equation that you will see is
2x + 2 = 6.
Part 1. Modeling the equation
1. The left side of the equation is 2x + 2.
a. How many x-cups will you need to model
this?
You will need 2 x-cups
b. How many unit counters will you need to
model this?
2 unit counters
c. Drag the correct number of cups and
counters to the left side of the equal sign
c. Drag the correct number of cups and
counters to the left side of the equal sign.
d. Click the “Check button” to make sure
you have the correct model.
This is the correct model for the
equation 2x +2 =6
Part II. Using your model to solve the equation
1. You first need to subtract the unit counters from the left
side and an equal number from the right side.
a. How many unit counters should be subtracted from
each side of the equation?
Subtracted one counter from the
left and one from the right sides.
Subtracted the last counter on the
left side and one from the right side.
b. Once you isolate the variables on one side of
the equation, you need to divide the remaining
unit counters so that there are an equal number
in each of the x-cups .
C.How many unit counters will be in each x-cup?
Check for Understanding with a new problem
Model and solve the equation 3x + 4 = 16.
3x + 4 = 16
3(4) + 4 = 16
12 + 4 = 16
16 = 16
The solution x = 4 is correct