S

in this equation 3/7x=18 What is x?

11 Answers
3/7x=18 What is x?
N

Hello Savior90 I'll do my best to help you with this algebra problem.


The original equality:

3/7x = 18



Multiply each side by 7x:

(3 * 7x) / 7x = 18 * 7x




Cancel out the 7x's [since 7x/7x = 1]:

3 = 18 * 7x



Clean up the rest of the numbers a bit:

3 = 126x



Divide both sides by 126 [and remove any instances where 126 / 126 = 1]:

3 / 126 = 126x / 126

3 / 126 = x * (126 / 126)

3 / 126 = x * 1

3/126 = x



Reverse equality for simplicity of style:

x = 3 / 126



If desired, calculate numerical value if preferred to fractional version:

x = 0.0238



In scientific notation that would be represented as:

x = 2.38 * 10^(-2)




You can (and should) check the answer by "plugging it back in" to the original equation:

3 / (7 * 0.0238) = 18

3 / 0.1666 = 18

18.007 = 18

when rounded to the proper number of significant figures the seven (7) is lost and the answer becomes:

18 = 18

So it checks out as a true equality!



Thanks for your question, and I hope this answers it fully for you. Please feel free to ask if you require any further assistance from me.

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N

I see where the source of the confusion is now. By default I would expect there to at minimum be a space between the the 7 and the x to even question whether or not the equality is written one way or another, I believe that means:

My answer would be correct for: -3 / (7x) = 18
Shardt97 and Sublim27 would be the correct answer for: -(3/7) * x = 18

Which would actually be better written as: -3x/7 = 18

If this makes sense, Savior90 then go with it! Otherwise, we would need a more precisely written form of this equation, or to somehow clarify it in the manner it was provided to you somehow! We could then give an exact answer from that information.

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P

Your question can be read two different ways.

(1) (3/7)x=18 which is the same as .42x=18
In this case x would be 42.88 after you divide 18 by .42

(2)

3
--- = 18
7x

In this case, you have to first multiply 7x by 18, which gives you 126x and then divide both sides by 126, which makes x equal to .0238

As a check
3
----------- = 18
(7 x .0238)

Therefore
3
------- = 18
.16666

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N
Sublim27 - Your answer does not seem to check out properly when plugged back into the problem.

3 / (7 * 42) = 18

3 / 294 = 18

0.010204081632653061224489795918367 =/= 18 (That should be a NOT EQUAL symbol between the two values)

I'm not sure where your problem is, but I believe I am correct, feel free to correct me if I am wrong - as I am not a mathematician! It is one of my weaker points in science.

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S

Multiply both sides by the reciprocal of 3/7, which is 7/3:

3/7x = 18
(7/3)(3/7)x = 18(7/3)

On the left side, a thing times its reciprocal is 1. On the right side, you can cancel: 3 into 3 once, 3 into 18 six times.

1x = 6(7)
x = 42

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S

X = 42

3/7 x = 18

(7) 3/7 x = (7) 18

3x = 126

X = 42

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S

3/7x=18

x=(18*7)/3

x=126/3

X=42

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S

3/7x=18

x=(18*7)/3

x=126/3

X=42

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G

3/7 x =8/1
= (3x*1) =7*8
=3x = 56
x =56/3

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S

X=(18*7)/3
x=42

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S

3/7x=18
X=42

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