Question 764432
Multiply left and right sides by abx.


{{{1/x + 1/a = 1/b}}}
{{{abx(1/x + 1/a) = abx(1/b)}}}
{{{ab+bx=ax}}}
{{{ax=ab+bx}}}
{{{ax-bx=ab}}}
{{{(a-b)x=ab}}}
{{{highlight(x=(ab)/(a-b))}}}