#### Answer

{12}.

#### Work Step by Step

$\frac{x}{3}$ = 4
Step 1: Multiply both the sides by 3
$\frac{x}{3}$ x 3 = 4 x 3
Step 2: Simplify
x= 12
Now we check the proposed solution, 12, by replacing x with 12 in the original equation.
Step 1: the original equation $\frac{x}{3}$ = 4
Step2: Substitute 12 for x
$\frac{12}{3}$ = 4
Step 3: Solve $\frac{12}{3}$ =4
4=4
Since the check results in true statement, we conclude that the solution set of the given equation is {12}.