1. ## SAT algebra equation

Hello Guys i was doing a Algebra SAT question.. and it was logical so i believe i got the right answer but in the future i don't want to get confuse so is there anyway to set an equation for this ?.

If 2x+2x+2x+2x=12 Then what is 2x-1=

I got that X is 2 because 2.2=4,2.2=4 2.2=4 =12 so 2.2-1=3

But i really don't know what would i ahve done if it was a bigger number..

2. $\underbrace{2x+2x+2x+2x}_{\text{Are there 3 or 4 of these?}}=12.$

3. $2x+2x+2x+2x=12 \implies 8x=12 \implies x=\dfrac{12}{8}$

now find 2x-1

4. Incidentally, you're in the right forum.

5. Originally Posted by Ackbeet
$\underbrace{2x+2x+2x+2x}_{\text{Are there 3 or 4 of these?}}=12.$
I got the book home but i am pretty sure is 3 of them because when i got 12 the only answer could been 3, 4's

6. $$\implies x=\dfrac{12}{8}$$ . You get 1.5

7. It makes a big difference if there are three or four of them. If there are three, then you're correct, and x = 2. You also correctly computed 2x-1, although your notation of using '.' for multiplication is not a good one for numbers. Use the asterisk: * for multiplication.

But i really don't know what would i ahve done if it was a bigger number..
If what was a bigger number?

8. The question should have $2x+2x+2x=12$.

Simple strategy: "Take a guess"

Try to take a reasonable guess for $x$. Let's try $x=3$. Then $2(3) + 2(3) + 2(3) = 6+6+6=18$, too big.

So let's try $x=2$. Then $2(2)+2(2)+2(2) = 4+4+4=12$. Just right.

So $x=2$ and $2x-1=2(2)-1=4-1=3$.

Note that you can do all of these computations quickly in your calculator.

After you're comfortable with the method of "guessing", also try to solve the problem algebraically.

9. Originally Posted by harish21
$2x+2x+2x+2x=12 \implies 8x=12 \implies x=\dfrac{12}{8}$

now find 2x-1
Originally Posted by Ackbeet
It makes a big difference if there are three or four of them. If there are three, then you're correct, and x = 2. You also correctly computed 2x-1, although your notation of using '.' for multiplication is not a good one for numbers. Use the asterisk: * for multiplication.

If what was a bigger number?
if that 2 and the 12 where bigger, is there any Equation i could use?

10. Originally Posted by DrSteve
The question should have $2x+2x+2x=12$.

Simple strategy: "Take a guess"

Try to take a reasonable guess for $x$. Let's try $x=3$. Then $2(3) + 2(3) + 2(3) = 6+6+6=18$, too big.

So let's try $x=2$. Then $2(2)+2(2)+2(2) = 4+4+4=12$. Just right.

So $x=2$ and $2x-1=2(2)-1=4-1=3$.

Note that you can do all of these computations quickly in your calculator.

After you're comfortable with the method of "guessing", also try to solve the problem algebraically.
Yea i did it over the method of logic , and guessing
but im trying to find it algebraically now

11. Originally Posted by vaironxxrd
if that 2 and the 12 where bigger, is there any Equation i could use?
Well, there's no equation. But there is a procedure:

$3x+3x+3x=21$

$9x=21$

$x=\dfrac{21}{9}=\dfrac{7}{3}.$

Then plug into your $2x-1$ expression to obtain

$2\left(\dfrac{7}{3}\right)-1=\dots$

12. Originally Posted by Ackbeet
Well, there's no equation. But there is a procedure:

$3x+3x+3x=21$

$9x=21$

$x=\dfrac{21}{9}=\dfrac{7}{3}.$

Then plug into your $2x-1$ expression to obtain

$2\left(\dfrac{7}{3}\right)-1=\dots$

I see you simplified the fraction So that would be 2*7 and 2*3 -1?

13. If you know how to factorise, you can make it a little simpler.

2x + 2x + 2x + 2x = 12

x(2 + 2 + 2 + 2) = 12

What is 2 + 2 + 2 + 2? It's 8 of course!

Then, x*8 = 12

x = 12/8 = 1.5

You can apply the same procedure for bigger numbers.

14. Originally Posted by vaironxxrd
I see you simplified the fraction So that would be 2*7 and 2*3 -1?
No, no. You multiply the scalar 2 times the fraction 7/3. THEN you add the fractions by getting a common denominator.

15. Originally Posted by Unknown008
If you know how to factorise, you can make it a little simpler.

2x + 2x + 2x + 2x = 12

x(2 + 2 + 2 + 2) = 12

What is 2 + 2 + 2 + 2? It's 8 of course!

Then, x*8 = 12

x = 12/8 = 1.5

You can apply the same procedure for bigger numbers.
yea it is 1.5 But if you do 2*1.5 you get 3 not 2*1.5-1

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