a) $\frac{3 x}{4}-\frac{2 x}{3}=\frac{1}{2}$

Step 1 ：Rewrite the equation with a common denominator of 12: \(\frac{9x}{12} - \frac{8x}{12} = \frac{1}{2}\)

Step 2 ：Combine the fractions on the left side: \(\frac{x}{12} = \frac{1}{2}\)

Step 3 ：Solve for x by multiplying both sides by 12: \(x = 6\)

Step 4 ：\(\boxed{x = 6}\)