Tomas can do a job in 4 hours. julia can do the same job in 6 hours. how many hours will it take the two of them to do the job if they work together?

Formula
job/time1 + job / time2 = job / t
 
job = 1
t = the time for both working together.
t1 = 4 hours
t2 = 6 hours
d = 1 job

1/t1 + 1/t2 = 1/t

1/4 + 1/6 = 1/t
find the lowest common denominator between 6 and 4

4 = 2 * 2
6 = 2 * 3

The lowest common denominator = 2 * 2 * 3 which is 12

3*1 / 4*3 + 2*1 / 2 * 6 = 1/t
3/12 + 2 / 12 = 1/t
5/12 = 1/t    Cross multiply
5t = 12 * 1     Divide by 5
t = 12 / 5
t = 2 2/5
t = 2.4 hours.<<<<<  answer

Notice that the time is less than 4 hours as it should be.

There is a formula for this:(Worker 1 * Worker 2) / (Worker 1 + Worker 2)(4 * 6) / (4 + 6) =24 / 10 =12 / 5 hours =2 (2/5) hours =2 hours 24 minutes

Multiply 9 and 67. then multiply 3 with 67. lastly the answer that you got for 9x67 is to be subtracted by the answer you got for 3x67