Question 57357
{{{1/x - 8/21 = 3/7x}}}
:
It's helpful to mult equation thru by the common denominator to get rid of the pesky fractions. 21x would be a good common denominator:
{{{(21x(1))/x - (21x(8))/21 = (21x(3))/7x }}}
That would leave you with:
21(1) - x(8) = 3(3)
:
21 - 8x + 9
:
subtract 21 from both sides:
21 - 21 - 8x = 9 - 21
-8x = -12
:
Divide both sides by -8 and you ave
  +1x = -12/-8
    x = +3/2
:
:
To check our solution in the original equation let's use 1.5 for 3/2
{{{1/x - 8/21 = 3/7x}}}
{{{1/1.5 - 8/21 = 3/7(1.5)}}}
.67 - .381 ~.289  close enough for checking