$$\frac{\frac{x}{3}-\frac{3}{3}}{x-1}$$
Since $\frac{x}{3}$ and $\frac{3}{3}$ have the same denominator, subtract them by subtracting their numerators.$$\frac{\frac{x-3}{3}}{x-1}$$
Express $\frac{\frac{x-3}{3}}{x-1}$ as a single fraction.$$\frac{x-3}{3\left(x-1\right)}$$
Use the distributive property to multiply $3$ by $x-1$.$$\frac{x-3}{3x-3}$$