Question 1140060
I assume you mean {{{(3/5)x-20=(x-20)2/5}}} , which I would write as
(3/5)x-20=(x-20)2/5 or 3/5)x-20=(x-20)(2/5) to avoid confusion.
 
The expression (3/5x -20) , means the same with or without parentheses. Those parentheses are not necessary.
To mean {{{(3/5)x}}} I would write is as (3/5)x, because sometimes 3/5x is interpreted as {{{3/"5 x"}}} or {{{3/5x}}} .
(The lack of any symbol or space between a number or variable is interpreted as if their product is in parentheses).
 
Multiplying times 5, both sides of {{{(3/5)x-20=(x-20)2/5}}} , we get the equivalent equations
{{{5*((3/5)x-20)=5*(x-20)2/5}}} ,
{{{5*(3/5)x-5*20=(x-20)*2}}} ,
{{{3x-100=2x-2*20}}}, and
{{{3x-100=2x-40}}}
Then, adding {{{100-2x}}} to both sides, we get the equivalent equations
{{{100-2x+3x-100=100-2x+2x-40}}} ,
{{{3x-2x=100-40, and
{{{highlight(x=60)}}} .
 
I hope you did not mean
{{{3/"5 x"-20=(x-20)2/5}}} , because that ends up being an uglier quadratic equation, with two ugly solutions.