I am going to solve a slightly different problem.

Solve for x where 2/3 - 1/4 x = 1/2

I would first look for a common denominator for all three fractions. The denominator I see is 3 4 = 12. At this point, rather than expressing each fraction with the denominator 12 I would multiply both sides of the equation by 12.

2/3 - 1/4 x = 1/2, so
12(2/3 - 1/4 x) = 12(1/2). Thus
8 - 3x = 6 and hence
3x = 2 or x = 3/2

Penny