Question 390896
First of all, finding the sum uses addition, so the problem: {{{5/6-3/4}}} will be a "difference" problem.

First, in order to find the difference between the two, you need to find a common denominator.

In this case, 6 and 4 are your denominators.  You must find a common multiple of these factors.  For example, 
4*3=12
and 
6*2=12
therefore, you can see that 12 is a common multiple of each number.

{{{(2/2)*(5/6)-(3/3)*(3/4)}}}
={{{10/12-9/12}}}
={{{highlight(1/12)}}}