Question 778263
-(4-a) means the opposite of (4-a).
6-(4-a) means 6+(-(4-a)).
6-(4-a) means 6+(-1)(4-a).
Take your pick.  Any of them may be used.  


The simplest for most people facing {{{6-(4-a)-2a}}} would be:
{{{6-4-(-a)-2a}}}
{{{6-4+a-2a}}}
{{{2+a-2a}}}
{{{2-a}}}