The assembly of a machine takes 3/4 hour there are 12 steps in the assembly process what is the average time for each step

We can solve this two different ways. I'll do both, and you choose which one makes the most sense:
We can divide the fraction 3/4 by 12. remember, when we divide fractions, we flip the second fraction and change the sign to multiplication:
3/4 ÷12     [starting equation]
3/4 x 1/12  [flip and change sign]
3/48    [now reduce]
1/16 Each step takes 1/16 of an hour. 
1/16 x 60 = 3 3/4, or 3.75 minutes

Second way:
3/4 of an hour is 3/4 of 60...45 minutes.
Still, we divide out:
45 ÷ 12   [starting equation]
3 9/12    [divide with remainder]
3 3/4 minutes...3.75 minutes