a) $\frac{2 n}{3}=4$
\(\boxed{n = 6}\)
Step 1 :Multiply both sides of the equation by 3: \(3 \times \frac{2n}{3} = 3 \times 4\)
Step 2 :Simplify: \(2n = 12\)
Step 3 :Divide both sides by 2: \(\frac{2n}{2} = \frac{12}{2}\)
Step 4 :Simplify: \(n = 6\)
Step 5 :\(\boxed{n = 6}\)