If 12 men can dig 35 holes in 14 days, (a) how many men are needed to dig 35 holes in 8 days? (b) How many days would it take 12 men to dig 30 holes?

Twelve men working 14 days is (12)(14) = 168 man-days.

a: If you have 8 days and need 168 man-days, then you need (168)/(8) = 21 men.

b: Thirty-five holes in 168 man-days is (168)/(35) = 4.8 man-days per hole, so 30 holes is (4.8)(30) = 144 man-days. Then you need (144)/(12) = 12 days to dig the holes.

Is that right? Thanks!