Question 54913
Multiply both sides by the LCD, which is 21:
{{{ 3x/7 - 5x/3 = 2/21}}}

{{{21*( 3x/7) - 21*(5x/3) = 21*(2/21)}}}


The nice thing is that ALL the denominators divide out:
{{{ 3*3x - 7*5x = 2}}}
{{{9x -35x = 2}}}

{{{-26x=2}}}


Divide both sides by -26:
{{{(-26x)/(-26) = 2/(-26) }}}


{{{x=-1/13}}}


Sometimes life comes out even, sometimes it does not.  In this case it looks like it does NOT!


R^2 at SCC