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 equation1. 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 problemModel and solve the equation 3x + 4 = 16.

3x + 4 = 163(4) + 4 = 1612 + 4 = 16

16 = 16 The solution x = 4 is correct