Question 660393
In order to add or subtract fractions, one has to get all the terms over a common denominator

 {{{((2d)/3)-((3d)/4)=(1/2)}}}
There are three denominators here. 3, 4, and 2. What is the smallest common multiple of 3,4 and 2?  Well, 12 is a multiple. So let's use that

We need to get all three fractions to have 12 as their denominator. We multiply each term by (1) (remember that 1 can be represented by any nonzero number divided by itself)


 {{{((2d)/3)-((3d)/4)=(1/2)}}}

 {{{(((2d)/3)*(4/4))-(((3d)/4)*(3/3))=((1/2)*(6/6))}}}
{{{(8d/12) -(9d/12) = 6/12}}}
{{{(-d/12) = 6/12}}}
{{{-d = 6}}}
{{{d = -6}}}