Question 777928
I believe the expression you have is
{{{20 - 6*4-3}}}
Normally, since multiplication takes precedence over addn/subtraction, you would
interpret it as {{{20 - 24 - 3 = -7}}}
However, a vinculum over (4-3) means that the expression under the vinculum (in
this case, 4 - 3) has to be evaluated first. 
So the expression is equivalent to {{{ 20 - 6*(4-3)}}}
={{{20 - 6*1 = 20 - 6 = 14}}}
Hope you got it :)