x does 1/4 of a job in 6 days. y completes rest of the job in 12 days. Then x and y could complete the job together in = ?

Answer: Option C

x does $$\frac{1}{4}$$ work in 6 days.
∴ x does complete work in 6 × 4 = 24 days
y does complete the $$\frac{3}{4}$$ work in 12 days.
∴ y does complete work in 12 × $$\frac{4}{3}$$ = 16 days
x and y together can complete a work in
$$\begin{array}{rl}& =\frac{16\times 24}{16+24}\\ & =\frac{48}{5}\\ & =9\frac{3}{5}\text{days}\end{array}$$