Explanation:

- P completes the task in 30 days.

- Thus, P's daily work rate = 1/30 of the work.

- Q is 50% more efficient than P.

- So, Q's work rate = 1.5 * (1/30) = 1/20 of the work per day.

- R completes the task in 10 days less than Q.

- Therefore, R's task completion time = 10 days, and R's work rate = 1/10 of the work per day.

- Q and R work together, so their combined daily work rate is 1/20 + 1/10 = 3/20 of the work.

- Together, they work for X days, completing 3X/20 of the task.

- The remaining work (1 - 3X/20) is completed by P in X + 8 days.

- So, the remaining work done by P is (1 - 3X/20) = (X + 8) * (1/30).

Calculate X:

$$1-\frac{3X}{20}=\frac{X+8}{30}$$

Let's solve for X:

$$30-\frac{90X}{20}=X+8$$

$$30-\frac{90X}{20}=X+8$$

$$600-90X=20X+160$$

$$600-160=20X+90X$$

$$440=110X$$

$$X=4$$

- The correct option is 4.

- Option:2, 4

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