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how to deal with two x's

can someone please help with this? I just can't get my head around it.

0.8 = 2 * x / (27 + x)

I need to find x...

thanks
Original post by chris238973
can someone please help with this? I just can't get my head around it.

0.8 = 2 * x / (27 + x)

I need to find x...

thanks


So, you've got x in the denominator and the numerator.

You want to get rid of the x in the denominator, so what could you multiply the whole equation by to do that? Any thoughts?
Reply 2
Original post by ghostwalker
So, you've got x in the denominator and the numerator.

You want to get rid of the x in the denominator, so what could you multiply the whole equation by to do that? Any thoughts?


that's what I'm thinking.

0.8 = 2x / (27 + x)
0.8 = x / 27 (dividing top and bottom by x)
x = 0.8 * 27
x = 21.6
Original post by chris238973
that's what I'm thinking.

0.8 = 2x / (27 + x)
0.8 = x / 27 (dividing top and bottom by x)
x = 0.8 * 27
x = 21.6


You can’t do that. Think of 2x and 27+x as being in brackets. You can’t just cancel through.
Try thinking of how to remove the fraction.
write the LHS as a fraction.... then use cross multiplication of fractions.
Original post by the bear
write the LHS as a fraction.... then use cross multiplication of fractions.


I wouldn’t be doing this either...
Reply 6
Original post by Jamie_1712
You can’t do that. Think of 2x and 27+x as being in brackets. You can’t just cancel through.
Try thinking of how to remove the fraction.


so would that work like this?

0.8 = (2x)/(27+x)
0.8*(27+x) = 2x
0.8x + 21.6 = 2x
21.6 =2x - 0.8x
21.6 = 1.2x
x = 12.6/1.2
x = 18
i thought you were suppose to multiply by (27+x) squared?
Original post by chris238973
so would that work like this?

0.8 = (2x)/(27+x)
0.8*(27+x) = 2x
0.8x + 21.6 = 2x
21.6 =2x - 0.8x
21.6 = 1.2x
x = 12.6/1.2
x = 18


Excellent. Well done. 😀
Reply 9
thanks

multiplied through by the denominator?
Original post by Jamie_1712
Excellent. Well done. 😀


thanks for your help!

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