E, F and G together can complete a work in 12 days. If E and F together can complete the same work in 30 days, then in how many days can G alone complete the same work?

LCM of 12 and 30 is 60. So we can assume the total work is 60 units.

E, F and G together can complete a work in 12 days.

The efficiency of E, F and G together = $$\frac{60}{12}$$ = 5 units/hour

If E and F together can complete the same work in 30 days.

The efficiency of E and F together = $$\frac{60}{30}$$ = 2 units/hour

Number of days taken by G alone to complete the same work = $$\frac{60}{5-2}$$

= $$\frac{60}{3}$$

= 20 days