How many 3/8 cup servings are in a pitcher containing 6 3/4 cup of orange juice?

You can solve this problem in multiple ways, but you'll have to divide the total volume with the amount per servings to find the number of servings (makes sense logically if you think about it).

The first way is to just use the fractions given. This will usually be your method in handling this if you're not familiar with it.

Convert 6 3/4 into an improper fraction. To do this, we need to put the 6 into the numerator somehow. We can approach this by multiplying the whole number (6) with the denominator (4) and adding it to (3). Basically, 6 x 4 + 3 = 27. This will be our new numerator. If you are not familiar with this concept, please let me know. 

Our new fraction for the total amount of juice is . Divide this with the amount per serving, 

 
We flip the second fraction over and multiply it.

(I crossed out common numbers here, unfortunately I don't know how to do that here so let me know if my explanation was not clear enough. I skipped a few steps.)

18 servings would be your answer.

Or you can convert 6 3/4 into decimal, which would be 6.75. 3/8 in decimal is .375 and you can do long division from there. That way is a bit more tedious in my opinion, but sometimes more convenient. 

Cheers!