7th Grade Math

COMPUTERS Adriana bought a computer and three pieces of software.

She spent a total of $1,220. The computer costs $995 and each piece of

software costs the same. Write and solve an equation to find the cost of

one piece of software.

What do you need to find? the cost of one piece of software

Draw a bar diagram to represent the situation.

Write an equation from the bar diagram. Let x represent the cost

of one piece of software.

3 x + 995 = 1,220

Use the work backward strategy to find the cost of one piece of

software. Since 3x + 995 = 1,220, 3x = 225 and x = 225 ÷ 3 or 75.

Each piece of software costs $75. Check 3 · 75 + 995 = 1,220 

the Results

3. How much more does the computer cost than the three pieces of software?


4. How would the equation change if she purchased the computer and three
   pieces of software during a sale in which she received one piece of software
   free with the purchase of two?

and Apply

BAR DIAGRAM Draw a bar diagram and write an equation for each situation.

Then solve the equation.

5. GROCERY Lindsey is buying a pound of cheese and 2 pounds of ham at the
   deli counter. The cheese is $3.99 per pound and her total cost at the deli
   counter is $14.97. What is the cost per pound of the ham?


6. MAIL It costs $0.42 to mail a letter. Jacob needs to mail a letter and
   3 packages having equal size and weight. The post office charges a total
   of $4.92. What is the cost of mailing each package?


7. E WRITE MATH Write a real-world problem that could be solved by the
   bar diagram.

Lesson 3A Multi-Step Equations 229

$1,220

$995???

computer software software software

600

450???

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