Since $x = 1/3$ is a root, then plugging $x = 1/3$ into every place $x$ occurs in your quadratic gives: $$p\left(\frac 13\right)^2 - 4\left(\frac 13\right) + p -2= 0$$
Solve for $p$.
$$\frac 19 p - \frac 43+ p = 2 \iff \frac{10}9 p = \frac 43 + 2 \iff p = \frac{9}{10}\cdot \frac {10}{3} = \frac 9 3 = 3$$
Since $x = 1/3$ is a root, then plugging $x = 1/3$ into every place $x$ occurs in your quadratic gives: $$p\left(\frac 13\right)^2 - 4\left(\frac 13\right) + p -2= 0$$
Solve for $p$.
$$\frac 19 p - \frac 43+ p = 2 \iff \frac{10}9 p = \frac 43 + 2 \iff p = \frac{9}{10}\cdot \frac {10}{3} = \frac 9 3 = 3$$