Arecipe calls for 2 1/2 cups of sugar. you have 2 1/3 cups of sugar. do you have enough sugar? if not, how much more sugar is needed? explain your answer

No not enough sugar I have
2 1/2 is more than 2 1/3 
For 1/2 (0.5) is more than 1/3 (0.333)
1/2 - 1/3 = 3/6 - 2/6 = 1/6
So we still need 1/6 of a cup of sugar

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