AHSME 1962 Problem 24

Three machines $\text{P, Q, and R,}$ working together, can do a job in $x$ hours. When working alone, $\text{P}$ needs an additional $6$ hours to do the job; $\text{Q}$, one additional hour; and $R$, $x$ additional hours. The value of $x$ is: $\textbf{(A)}\ \frac{2}3 \textbf{(B)}\ \frac{11}{12} \textbf{(C)}\ \frac{3}2 \textbf{(D)}\ 2 \textbf{(E)}\ 3$