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SAT Linear Equations in One Variable Question 97 | Free SAT Prep | Aniko

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Question 97·Easy·Linear Equations in One Variable

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If $8x - 4 = 20$ , what is the value of $2x$ ?

Your answer

(Express the answer as an integer)

For linear equations like $8x - 4 = 20$ , quickly isolate the term with $x$ by undoing addition or subtraction, then solve for $x$ by dividing by the coefficient. Finally, re-read the question to see what expression they actually want (such as $2x$ or $3x - 1$ ) and plug in your value of $x$ —this prevents errors where you stop too early or report the wrong quantity.

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Isolate the $x$ term

Think about how to get rid of the $-4$ on the left side of $8x - 4 = 20$ . What operation will cancel $-4$ ?

Solve for $x$

After you isolate $8x$ on one side, what should you divide both sides by to get $x$ alone?

Answer the actual question

Once you know $x$ , make sure you compute $2x$ , not just stop at the value of $x$ .

Desmos Guide

Use Desmos to compute $2x$ directly

In a Desmos expression line, type:

2 * \left(\frac{20 + 4}{8}\right)

Desmos will display a single numerical value; that value is the value of $2x$ for the equation $8x - 4 = 20$ .

Step-by-step Explanation

Undo the subtraction to isolate the $8x$ term

Start with the equation:

8x - 4 = 20

To get $8x$ by itself, add $4$ to both sides:

8x - 4 + 4 = 20 + 4 \\[0.7em] 8x = 24

Solve for $x$

Now isolate $x$ by dividing both sides of $8x = 24$ by $8$ :

x = \frac{24}{8} = 3

This gives the value of $x$ , which you will use to find $2x$ .

Find the value of $2x$

You are asked for $2x$ , not just $x$ . Substitute $x = 3$ into $2x$ :

2x = 2 \cdot 3 = 6

So, the value of $2x$ is $6$ .

Strategy

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Desmos Guide

Step-by-step Explanation

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Strategy

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Desmos Guide

Step-by-step Explanation