i'm trying to work out what steps i need to take to calculate the number that makes the following true...

(719 + 728 + 692 + 719 + X) / 5 = (719 + 728 + X) / 3

i know the answer is about 670 but don't know how to work it out.

can anyone help?

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- Aug 15th 2010, 12:46 AMval1trying to work out what probably is a pretty basic formula. (solved)
i'm trying to work out what steps i need to take to calculate the number that makes the following true...

(719 + 728 + 692 + 719 + X) / 5 = (719 + 728 + X) / 3

i know the answer is about 670 but don't know how to work it out.

can anyone help? - Aug 15th 2010, 12:50 AMProve It
First it would help if you'd learn some LaTeX, so people can actually read what you've posted...

I assume it's

$\displaystyle \frac{719+728+692+719+x}{5} = \frac{719+728+x}{3}$

$\displaystyle \frac{2858+x}{5} = \frac{1447 + x}{3}$

$\displaystyle 3(2858 + x) = 5(1447 + x)$

$\displaystyle 8574 + 3x = 7235 + 5x$

$\displaystyle 1339 = 2x$

$\displaystyle x = 669.5$. - Aug 15th 2010, 01:12 AMval1
ok, sorry about that. but that's excellent, i can see what i needed to do. i appreciate that a lot.