You can assemble a shelving unit every 30 minutes. at this rate how long would it take you to assemble 9 shelving units?

9 shelving units is 9 times 1 shelving unit.

If it takes 30 minutes to assemble one shelving unit, it would take 9 times that amount to assemble 9 of them. Multiply 9 by 30 to get your answer in minutes. If you need your answer in hours, since there are 60 minutes in an hour, take the amount of minutes it took and divide it by 60. 

(6,0) i hope it makes enough sense