A, B and C together can complete a work in x , 30 and 45 days, respectively. B and C worked together for 6 days. The remaining work was completed by A alone in 12 days. The value of x is:

18

A = x days, B = 30 days, C = 45 days,

⇒ B + C worked for 6 days = (3 + 2) x 6 = 5 x 6 = 30 units,   ..(Efficiency × Days = Work)

⇒ Remaining work = 90 - 30 = 60 units,

⇒ A completed the remaining work in 12 days = \(\frac{60}{90/x}\) = 12 days,

⇒ x = 18.