To transform a mixed number to an improper fraction, we must multiply the denominator by the large number, and add the numerator.
So for :
But we also put this over the denominator in the mixed number, so we get: .
Then we do the same for :
Then we must find a common denominator. Let's use 21 (multiply 3 and 7):
Now that we have a common denominator, we can subtract across:
Since cannot be reduced any further, we are going to leave this as our answer.
So the answer is .